COST C16
Improving the Quality of Existing Urban Building Envelopes
STRUCTURES
Research in Architectural Engineering Series Volume 4 ISSN 1873-6033 Previously published in this series: Volume 3. E. Melgaard, G. Hadjimichael, M. Almeida and L.G.W. Verhoef (Eds.) COST C16 Improving the Quality of Existing Urban Building Envelopes – Needs Volume 2. M.T. Andeweg, S. Brunoro and L.G.W. Verhoef (Eds.) COST C16 Improving the Quality of Existing Urban Building Envelopes – State of the Art Volume 1. M. Crisinel, M. Eekhout, M. Haldimann and R. Visser (Eds.) EU COST C13 Glass and Interactive Building Envelopes – Final Report
COST C16
Improving the Quality of Existing Urban Building Envelopes
STRUCTURES
edited by: Roberto di Giulio Zivko Bozinovski Leo G.W. Verhoef
IOS Press
© 2007 IOS Press and the Authors. All rights reserved ISBN 978-1-58603-736-9 Published by IOS Press under the imprint Delft University Press Publisher IOS Press BV Nieuwe Hemweg 6b 1013 BG Amsterdam The Netherlands tel: +31-20-688 3355 fax: +31-20-687 0019 e-mail:
[email protected] www.iospress.nl www.dupress.nl LEGAL NOTICE The publisher is not responsible for the use which might be made of the following information PRINTED IN THE NETHERLANDS
v
Table of Contents Preface L.G.W. Verhoef Introduction R. Di Giulio
vii 1
Changing Image The Utrillo Building Rehabilitation Project F. Allard, G. Guarracino, D. Groleau Change of Identity of “Geldershoofd” in Amsterdam – Bijlmermeer L.G.W. Verhoef, M. van der Lubbe, A. uit den Boogaard Techniques for Adaptations of the Structures of a Multi-storey Family House in Florence R. Di Giulio, S. Brunoro, P. Civiero
5 15 27
Upgrading Functionality A Future for WBS 70; The Franz-Stenzer Building Block as Case Study W.J. Quist Creating Flexibility for Better Use of Space in Dwellings in Multi-storey Buildings L.G.W. Verhoef , N. Hendriks, H. van Nunen, R. Laurs Restoration of the ‘Planeten flats’ in Helmond L.G.W Verhoef, F. Maas, J. van der Boomen Rebuilding Modern Housing for Increased Sustainability S. Vidén Enlargement of Balconies and Upgrading of Existing Residential Building Daskal Kamcev street number 1 in Skopje Z.L. Bozinovski, K. Gramatikov Enlargement of Balconies of Existing Residential Building “Karpos” in Skopje K. Gramatikov, Z. L. Bozinovski Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope - Malta R.P. Borg
37 51 59 69 81 91 99
Additions to Existing Buildings Adding an Extra Storey J. Engelmark, T. Dahl, E. Melgaard New Facade Combined With Inside Rebuilding J. Engelmark, T. Dahl, E. Melgaard Reconstruction, Enlargement, Adding Storeys and Revitalization Z.L. Bozinovski, K. Gramatikov Adding Two Stories to Existing Building A. Kozáowski, Z. Plewako, A. Rybka Annex of Attics on Flat Roofs of Urban Residential Buildings A. Krstic-Furundzic Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands M.T. Andeweg, F.W.A. Koopman
111 119 125 133 141 151
vi
Restrengthening Adaptations and Improvements on a Refugee Estate in Cyprus Ch. Efstathiades, G. Hadjimichael, P. Lapithis Externally Bonded Steel or Carbon Fibre Reinforcement F. Van Rickstal, W. Figeys, K. Brosens, D. Van Gemert Balconies, Loggias and Different Thin-walled Units in Large Panel Buildings K. Wróbel, W. Kubiszyn
161 173 179
Recycling Recycling Prefabricated Building Components for Future Generations C. Asam Reuse Possibilities of Dismantled Building Elements from Pre-fabricated Concrete Buildings C. Asam Typical Measures on Load Bearing Building Elements During Modernisation C. Asam
187 195 203
Improving Safety Safety Evaluation of External Sandwich Panels in Large-panel Buildings A. Kozáowski, A. Rybka, Z. Plewako Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes J. Šelih, B. Dolinšek, R. Žarniü Conclusions Z.L. Bozinovski
211 221
233
Annex COST C16 Management Committee
237
COST C16 Working Group Members
241
vii
Preface
In front of you lies one of the four books produced within the scope of Action C16 “Improving the quality of existing urban building envelopes” which started as a COST UCE programme. The acronym ‘COST’ stands for European COoperation in the field of Scientific and Technical research, and falls under the Urban Civil Engineering Technical Committee (UCE). The main characteristic of COST is a ‘bottom-up approach’. The idea and subject of a COST Action comes from the European scientists themselves. Participation is open to all COST countries but only those countries that wish to participate in an Action do so. As a precursor to advanced multidisciplinary research, COST has a very important role in building the European Research area (ERA), anticipating and complementing the activities of the Framework Programmes, acting as a bridge between the scientific communities of emerging countries, increasing the mobility of researchers across Europe and fostering the establishment of large Framework Programme projects in many key scientific domains. It covers both basic and applied or technological research and also addresses issues of a pre-normative nature or of societal importance. The organisation of COST reflects its inter-governmental nature. Key decisions are taken at Ministerial conferences and also delegated to the Committee of Senior Officials (CSO), which is charged with the oversight and strategic development of COST. The COST Action C16 “Improving the quality of existing urban building envelopes” is directed to multi-storey residential blocks from the period after World War II, especially those built during the period when the need for housing in Europe was at its greatest. That is why the COST Action C16 focussed on the period 1950 to 1980. We found it necessary to propose this Action after the completion of Action C5 “Urban heritage/building maintenance”. According to studies carried out by Action COST C-5, the estimated value of the European Urban Heritage amounts to about 40 trillion Euro (1998 prices) for the housing stock alone. The same research indicated the differences between the countries of the EU as well as what they have in common. The age profile of the building stock of a country like the Netherlands differs from that of the UK. Of interest too, are the costs of maintenance, renovation and refurbishment of the building stock. For the EU as a whole, this amount is about 1 trillion Euros per year (1998 prices). At the same time the three ‘Building Decay Surveys’ issued by the Federal Government of Germany that were based on systematic, scientific building research projects, indicated that 80% of all building decay is found in urban building envelopes (roof, walls, foundation). There are elements in the building stock that are common to the countries in Europe. These include: Most of the buildings were completed after 1950. For a country like the Netherlands this means 75% of the existing buildings. The maintenance costs are mainly incurred in urban building envelopes, The renovation of buildings and reconstruction to provide an improved or different range of use will influence the building envelope, The quality of the building envelope very often fails to meet current demands and will certainly not meet future demands.
viii An important conclusion deriving from the points mentioned above is that however important maintenance may be, it does not lead to the desired improvement in the quality of urban building envelopes. Improvement of the quality of urban building envelopes must be the real task. Such improvement requires the development of new and suitable strategies for local authorities, housing corporations and owners and also architects and civil engineers. Until now integrated engineering aspects have been disregarded in this process. In many European countries new technologies have been developed, but these have either not yet been translated into practice, or have been only locally used to achieve a higher quality in urban buildings. This results in a limited impact on urban environments. Therefore it is essential to bring all kinds of local solutions together, to learn from these and to find a more general approach that can be used for building systems. Often problems and their solutions are approached in isolation. The wish to improve the quality of an individual building envelope usually leads to a local, project-based solution. Solving the specific problems of this renovation-project becomes the sole target. To reach maximum value for money, it is essential to integrate all the factors influencing urban building envelopes and look at them in a broader scope. As a result of changes in the composition of the population, society continuously changes with respect to various factors including age-structure, family composition and the availability of energy. Changes lead to situations that are reflected in the commissioning of buildings, which is gradually shifting from new construction to the reuse and renovation of existing buildings that often requires the modification of their facades. Even when buildings may still be functionally satisfactory, there may be external factors, such as the dullness of the image that they summon up or their poor technical quality, that require that attention should be paid to the shell of the building. There are many reasons why buildings may no longer be adequate. Failure to satisfy current demands may be expressed in lack of occupancy and further deterioration of the neighbourhood. This establishes a vicious circle, which can and must be broken. All too quickly discussions turn to demolition and new development, without prior investigation of the reasons for the situation. From an economic point of view, renovation and the reuse of buildings, which takes into consideration the technical and spatial functions and also the urban and architectural aspects, often appears to provide a better solution. The aim of the COST Action C16 is to improve techniques and methods used to adapt the envelopes of buildings constructed during the second half of the 20th century in the COST countries. These ‘non-traditional buildings' were constructed from in situ poured concrete systems, large scale prefabricated systems and/or small concrete/mixed elements although in some countries brick or stone was still used. The demand for housing in the post-war period necessitated the rapid production of large numbers of dwellings. Qualitative aspects were less important. Furthermore dwellings of the types constructed at that time no longer fulfil contemporary or anticipated future demands for housing, with the possible exception only of those built during the last 5 years. At this stage, it must be noted that two other ongoing Actions in the field of Urban Civil Engineering, also address issues related to buildings: COST Action C12 on “Improving buildings’ structural quality by new technologies”; and COST Action C13 on “Glass and interactive building envelopes”. The Technical Committee on Urban Civil Engineering considers that in addition to the tasks directly connected to the main objective of their Action, participants in the COST Action on “Improving the quality of existing urban building envelopes” should establish and maintain close contacts with the two above mentioned Actions. This will foster co-operation with these Actions and avoid potential overlaps. About one year after the start of COST Action C16, it was put on a hold for more than 8 months, to permit the ‘renaissance’ of the COST programmes, while in the meantime COST C12 had almost ended and it was considered that the C13 Action had only a slight connection
ix with the targets of COST C16. The CSO therefore agreed with the request of the Management Committee that the end of this Action should also be postponed by 8 months so that it would still last for the planned duration of four years. SCIENTIFIC PROGRAMME To date problems relating “Urban Building Envelopes” and their solutions are approached in isolation. The original design planners, architects and engineers work together to realise a building according the current state of knowledge, but this co-operation longer exists during the lifecycle of the building. For far too long prolongation of the occupation by the use of maintenance was sole aim. If improvement did become an option only a few aspects were considered. At present the current state of knowledge is usually local, being concentrated in some of the housing co-operations, architectural and engineering companies. However much has been done to spread this information in order to initiate discussion about when and how existing buildings with their envelopes can be improved to fit them for the future. The COST mechanism will foster international concentration on the integrated problems related to non-traditional dwellings. It will create a direction for improvement of urban building envelopes and also illustrate the state of the art in the various countries concerned.. What has already been learned in one country can now easily be shared or can be translated to fit the needs of other countries. His will make the implementation of new practices much easier. The World Wide Web will be used to bring all the information on the major non-traditional housing systems in Europe together as well as the various techniques for the improvement of urban building envelopes. We are happy to announce that for the first time since the establishment COST, it has become possible not only to publish books but to place the information on the World Wide Web. See www.costc16.org. High schools and universities interested in the subject of the renovation of existing buildings can now have east access to this knowledge. This study was based on the following scientific programme: Description and analysis of the types of system related to the factors influencing urban building envelopes; Analysis and comparison of the legislation and technical regulations relating to renovation in European countries; Analysis of how urban building envelopes have been changed to date in relation to relevant factors; A survey of existing engineering techniques that can be used, modified or developed to reach this goal; A synthesis of possible global approaches leading to guidelines on how to reach maximum value for money in relation to the desired quality and working conditions in the urban environment and also how this approach can be reached for other types of buildings. THE SCHEME OF THE APPROACH OF ACTION C16 The original idea given in the technical annex of the Action was to start with a preliminary approach lasting six months. After that, three working groups would be set up on the themes of: the current envelopes, the needs and the techniques. A period of three years was allocated for this. The last six months of this period would have been used to integrate the result of the working groups and to prepare the final international symposium. As stated above, one year after the start of the Action C16, together with other Actions, was placed on hold, because of the reorganisation of the COST organisation to create an umbrella organisation. At the beginning of 2004, on the basis of the contract between the European Science Foundation and the European Commission for the Support of COST, this reorganisation started with the establishment of the fully operative COST office in Brussels.
x This delay caused to loss of some momentum. A second problem that had to be solved was that the members of C16 came from a variety disciplines and included structural engineers, architects and physicians. Although an interdisciplinary approach is one of the targets of a COST Action, this did give rise to problems in the working group on techniques. For example bearing structures demand a different specialisation from that required for secondary elements, such as facades and roofs. The management committee was wise in its decision to split the Techniques Working Group into a working group on structures and a working group on facades and roofs. THE METHODOLOGY The methodology used for the work of the four working groups of the Action C16 “Improving the quality of existing urban building envelopes” differs. The first book entitled ‘The state of the art’ is divided into two parts. The first part comprises a survey on the housing stock for each country. It contains data related to the building period, main typology and technologies. In the second part the topics covered describe the quality of the housing stock. The ‘state of the art’ depends on the time at which a survey takes place. That is why we consider it an advantage to also publish the two keynote lectures in this first book. These describe approaches to the modification of the multi storey family stock that is currently under investigation. In the second book, ‘The needs’, the method used to obtain precise information was to develop a table that includes the needs, solutions and priorities for each country. It is evident that these needs and priorities will differ greatly from country to country, as illustrated for example by comparing Sweden to Malta. To determine these aspects, criteria such as land use, architectural aspects and building physics are used, as well as aspects relating to finance and management. In the third book, ‘Structures’, a framework for possible solutions has been set up. It contains 20 case studies in which changes in bearing structures to fit for future purposes was the goal. Examples include descriptions of how to build extra floors onto existing buildings for both financial reasons and also to make the installation of elevators more profitable.. Another example illustrates the need for greater flexibility, and shows how a part of the bearing structure can be changed to provide this. In the fourth book, ‘Facades and roofs’, which is based on the results of the working groups’ The state of the art’ and ‘Needs’, two documents have been developed, ‘Technical Improvement of housing Envelopes’ and ‘Country Criteria in the form of a matrix’. Relations between the most frequently used refurbishing solutions and their impact on sustainability have been worked out in depth. Sustainability is described in a set of performances such as, technical, economic, functional/social and environmental. Case studies illustrate these theories. Together these books provide much information and can help countries and people to learn from each other. It is my wish that that you will all profit from their content. Leo G.W. Verhoef (Chairman COST Action C16) April 2007
Introduction Roberto Di Giulio Chairman of Working Group 3A Department of Architecture, University of Ferrara, Italy
This publication brings together the results of the work carried out by the Working Group 3A (WG3A) which, as part of the Action Cost C16 research programme, worked on the theme of “Techniques of adaptations of the structure of multi-storey family houses in relation to Urban Building Envelopes”. The WG3A dedicated particular attention to the most widespread technology and innovative trends in terms of building methods and techniques used in the modification, restrengthening or adaptation of the structure affecting the building envelope components. Following on from the initial analysis and discussion of the documents, research and case studies, the state of the art and innovative processes currently in use, it became clear that the situations in the various countries differed significantly due to various factors of a political and technical nature. The differences deriving from political factors depend on the diversity of requirements and the objectives at the basis of the property regeneration, reuse and valorisation policies. The very characteristics of the properties in question had a significant influence on the choice of priorities and the most suitable operating technologies. Large buildings, particularly those in Eastern countries, constructed using heavy prefab systems and procedures targeted at the fast and low-cost satisfaction of the demand, rather than at the quality of the accommodation, impose priorities that differ greatly from those in situations in which an acceptable standard of quality makes it possible to focus on improving factors such as the functionality of the residential units, the energy efficiency of the buildings, the architectural quality of the buildings and the quality of life in the residential districts of the urban outskirts. In contexts in which the priority is to meet basic quality standards, such as the regeneration of rundown areas or the restoration of basic safety conditions, experimentation with innovative technology is implemented on the basis of different schedules. Naturally, this does not entail a lack of research and development. However, in these cases, the nature and extent of the work needed often requires the use of basic technology and traditional solutions, significantly restricting the space for experimentation in the more advanced sectors. On the other hand, the differences deriving from technical factors depend on the often evident differences that characterise the industrialisation levels of the building sector and the organisational models on the basis of which the production process is implemented. These differences have a substantial influence on the demand for innovation, on the market at which this innovation is targeted and, consequently, on the public and private resources invested in the research and development sector. In this case too, there is an evident diversity in the dynamics of the innovation processes and in the sectors, which may have evolved to a different degree in each country, thus characterising the regeneration programme management policies and the operating strategies. When faced with the numerous situations described above, it became evident that it would be difficult to present a detailed and exhaustive picture for each country, relative to the technology and techniques used for all the various operations on the structural components that, in some way or another, involve the building envelopes.
2
Introduction
This would have been an extremely vast field of research. Structural problems in buildings almost always involve evident interdependence on the components of the building envelope. In some cases, such as load-bearing panel buildings, these problems coincide. The work group therefore chose to analyse the situation in the various countries and to draw up a profile of current trends, through the presentation of a series of case studies selected from amongst those most emblematic and representative of each national context. The contributions collected and featured in this volume therefore represent a selection of experiences gained or underway in relation to the technology, materials and building techniques used in the transformation, restoration or regeneration of multi-storey family houses in which aspects of a structural nature prevail. As already mentioned, the documentation and analysis phase revealed that highly diverse situations are in place in different areas of the community. Alongside countries where the recovery and regeneration policies respond to quality standard improvement and building valorisation requirements, there are also situations in which the objectives are restricted to the restoration of static safety conditions, seriously prejudiced by advanced dilapidation, or to the satisfaction of basic habitation requirements. Between the two extremes we find a series of situations in which the choices and priorities have been dictated by natural disasters or by particular socio-political conditions. The main operating strategies relative to the case studies collected and documented by the WG3A, include: - changing image, targeted at the general regeneration of peripheral or marginal urban contexts; - upgrading functionality, involving changes to the intended use, the transformation of the layout, the resizing of the residential units, etc. - additions to existing buildings involving the development of new volumes; - restrengthening work; - experimental reuse and regeneration work involving the recycling of dismantled components; - improving safety. Changing Image Work that entails the transformation of the morphology of the building envelope and its architectural image is usually carried out as part of a regeneration programme that does not just involve the building itself, but the quality of the residential conditions and services of entire urban areas. For example, in the French case study1, the modifications made to the facades of the property in La Rochelle were also designed to break up the uniformity and monotony of the urban landscape and boost the distinguishing features of the individual residential units, as well as to regenerate the building. The work on the “Geldershoofd building” in Amsterdam2 and the buildings in “Le Piagge” district of Florence3 also had the objective of giving a “new identity” to the large residential estates characterised by an anonymous and impersonal architectural image. As in the French case, the technical conditions of the buildings were not particularly prejudiced in these two cases. The requirements expressed by the users in relation to the aesthetic and functional quality of the accommodation were not fully satisfied. The response to this need was resolved, in both cases, by creating new types of accommodation (resized on the basis of the new user profiles), by transforming the layouts, introducing new uses inside the buildings alongside the residential ones, and radically modifying the facades and the volumes of the buildings. Even when not directly related to the transformation of the buildings, the structural work involved complex restrengthening operations and the adaptation to the new static configuration of the buildings in all cases. In the Italian case in particular, the restrengthening of the loadbearing structures was needed in order to bring the building into line with new aseismic regulations.
Introduction
3
Upgrading Functionality Numerous case studies regard work on the facades and structure as part of projects relative to the regeneration of the interiors. In these cases, the transformation of the building envelope consists of the adaptation of the latter to the modifications to the layout. In many cases, these modifications consist of the creation of new openings in the facades in order to adapt to the new ventilation and lighting requirements imposed by the new layout of the interiors, the inclusion of new structural elements in order to make the accommodation more flexible, and the development of new additional spaces achieved by extending (or constructing from scratch) balconies and galleries. Most of the functional upgrading operations described in the case studies have these objectives, in the desire to seize the opportunity to make general improvements to the architectural quality of the individual buildings and a contribution to the valorisation of the residential districts. The case of the large complex in the Berlin district of Marzahan4 is particularly interesting. The poor flexibility of the prefab structures made from large load-bearing structures led to experimentation with complex structural solutions, which permitted radical transformations to the facades, reducing the quantity of load-bearing panels to be demolished to a bare minimum. Another problem faced during the functional upgrading projects was the improvement of facilities for the disabled and the elderly. The accesses (entrances, atriums, stairwells, etc.) and the dimensions of certain service areas in the accommodation make a significant contribution to achieving this objective and entail major work on the building envelope and the structure. In the case of the work carried out in the Markbacken5 residential district in Örebro (Sweden), for example, improvements to disabled access is one of the strategic elements of the project. The solutions adopted were concentrated on the entrance and horizontal and vertical connection zones (stairs, corridors, lifts), the balconies, which were extended or built from scratch, and the transformation of the accommodation layout. Additions to existing buildings Additions to existing buildings are of particular interest, especially due to the innovative elements that can often be found in the technology used. These interventions concern both façades and roofs. In both cases, the partial demolition work and the subsequent insertion of new sections of building, are carried out with industrialised procedures which use technologically advanced building solutions, components and materials. With the roof work, as well as improving the building's energy performances and having the possibility to make radical transformations to the architectural image, there are also additional advantages connected with the substantial increase in living surfaces that can be created. The creation of an extra storey with new living areas on existing social housing blocks does, in fact, allow an average increase in living space that can vary between 15% and 25% of the total surface area. Both action strategies have been shown through some Danish case studies. In the local area of Rødovre, just outside Copenhagen6, the work that was needed due to roof degradation caused by the poor quality of the tile covering, provided the opportunity to carry out radical redesigning of the building, as well as remaking the sealing layer, which brought about a definite improvement in the energy efficiency and a consistent increase in the number of living areas. The removal and replacement of an entire portion of a building in the centre of Copenhagen7, on the other hand, was purely functional. In this case, the addition consisted of the insertion of prefabricated bathroom and kitchen blocks in order to improve the functional quality of 19th century residences without certain facilities. Finally, the work carried out in Belgrade8 on attics that were not suitable for residential use and that were completely readapted was very interesting. The building solutions, based on the use of wooden structural elements, used the original criteria of the “overlapping” of a light structure on the reinforced cement structures of the buildings.
4
Introduction
Restrengthening Work aimed at reinforcing degraded structural elements, or that have been weakened by the deterioration of materials, are more common and are generally carried out using traditional techniques. In situations where the interventions have to cope with a sudden and substantial increase in demand, the main objective is to focus on the safety and habitability conditions. The case study in Cyprus9 showed shows more carefully planning however; without causing conflicts with the limits imposed by climatic and financial factors, it was possible to add various significant quality elements, such as: the introduction of architectural character in the buildings through the diversification of the façades, the improvement in levels of accessibility for disabled people and a more functional distribution of the internal areas. Recycling An interesting application of the principles of a sustainable approach in the development of urban recycling and redevelopment is shown in the German case studies10. Experimental technology and procedures were applied for reusing prefabricated elements removed from residential buildings destined for partial or total demolition (in Germany – in particular in the eastern area – 350,000 residential buildings are due to be demolished by 2020). The operation consists of recycling the concrete floor slabs, which can be reused as structural elements in rows of houses. Obviously the techniques of demolition and disassembly of components are of paramount importance for keeping panels integrity. Improving safety The last type of work examined by the WG3A concerned consolidation work carried out in countries hit by natural disasters in order to restore or improve the structural safety conditions of the damaged buildings. The Slovenian case study11, in particular, shows the techniques used for repairing the damage caused by the 2004 earthquake and the solutions used to reinforce the external load-bearing walls with details aimed at improving performance in the case of future seismic events. 1
F.Allard, G.Guarracino and D.Groleau, The Utrillo Building Rehabilitation Project. L.G.W. Verhoef, M. van der Lubbe & A. uit den Boogaard, Change of Identity of “Geldershoofd” in Amsterdam. 3 R.Di Giulio, S.Brunoro, P.Civiero, Techniques for adaptation of the structures of multi-storey family house in Florence. 4 W.J. Quist, A future for WBS 70The Franz-Stenzer building block as a case study. 5 S. Vidén, Rebuilding modern housing for increased sustainability. 6 J. Engelmark, T. Dahl & E. Melgaard, Adding an extra storey. 7 J. Engelmark, T. Dahl & E. Melgaard, New facade combined with inside rebuilding. 8 A. Krstic-Furundzic, Annex of attics on flat roofs of urban residential buildings. 9 Ch. Efstathiades, G. Hadjimichael and P. Lapithis, Adaptations and improvements on a refugee estate in Cyprus 10 C. Asam, Recycling prefabricated building components for future generations. 11 J. Šelih, B. Dolinšek & R. Žarniü, Refurbishment of multi-storey residential building in relation to the Building Envelopes 2
The Utrillo Building Rehabilitation Project Francis Allard LEPTAB, Université de La Rochelle, France
Gérard Guarracino DGCB, Ecole Nationale des Travaux Publics de l’Etat, Vaulx en Velin, France
Dominique Groleau Cerma, Ecole Nationale Supérieure d’Architecture de Nantes, France
ABSTRACT: This paper describes the rehabilitation project of the Utrillo Building located in La Rochelle, France. The present project has been launched within the national frame of Urban Renovation Plan. It does not consist only of the building rehabilitation, but it aims at a real urban renovation replacing the buildings in a new urban scenario. In the present paper we will focus mainly on the structural aspects of this rehabilitation project.
1 GENERAL DESCRIPTION OF THE CASE STUDY 1.1 Location of the project The Utrillo building is located in the Mireuil district of La Rochelle. It is a property of “OPHLM de La Rochelle”, a Public Social Housing Society. It is an example of the social architecture of the end of the sixties. Built in 1968, it needs now a strong rehabilitation which aim is not only to improve the building itself but to change, its social and architectural image. This project is included in a more general frame of urban renovation of socially sensible neighborhoods (ZUS) supported by ANRU (National Agency for Urban Renovation). These programs aim at a general environmental and social recovery of these neighborhoods associating, urban, environmental, social and architectural objectives. Figure 1 presents a plan view of the location
Figure 1: General location of the Utrillo building.
This building built in 1968 is 230m long with 9 levels and a total of 233 apartments. COST C16 Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
6
The Utrillo Building Rehabilitation Project
1.2 General objectives of the project The present renovation is associating three main goals: A substantial modification of the building morphology by breaking down its uniformity an d identifying clearly various housing units: 2 slots and 3 arches are planned through the building, creation of two adjacent buildings and penthouse apartments. A real reinsertion of the building in its social and urban environment, A new allocation of spaces enabling a clearer definition of uses, improving the appropriation by the users, improving the security and creating smaller housing units with a clear identity. 2 PROBLEMS CONCERNING THE STRUCTURE
2.1 Typology of the structure 2.1.1 Façades Built at the end of the sixties, this building is a good example of the heavy prefabrication method used in France at this time. Figures 2 (a & b) shows the main two façades of the existing building,
(a)
(b)
Figure 2: General views of the façades of Utrillo building
The Utrillo Building Rehabilitation Project
7
2.1.2 Foundations As a good soil is founded at a low depth, (around 2m) The building has only superficial foundations. Figure 3 shows the foundation principle.
Figure 3: Superficial foundations of the Utrillo Building
2.1.3 General Structure The general structure of the Utrillo building is made of prefabricated elements (walls and ceilings). The wall elements are 2.53 meter high. Three different thicknesses of walls are used: 14 cm for partition walls, 29 cm for walls located near the dilatation joints and 25 cm for the façades. All these walls are simply assembled together by a pin system. This gives to the general structure a modular architecture of regular elements. Each unit connected to two staircases represents 32 apartments.
Figure 4: Modular element of the structure
2.2 Problems concerning the structure This structure is in a good general state. No important disorder has been found. The only structural problems are related to corrosion problems specifically at the balconies (fig. 5a) or at the junction between walls and balconies (Fig. 5b).
8
The Utrillo Building Rehabilitation Project
(a)
(b)
Figure 5 : Examples of corrosion effects on the external balcony structure (a) and at the junction between wall and balcony (b)
All the problems due corrosion should be cured during the general rehabilitation of the building. Other elements as fluid networks or conformity to fire regulation will also be checked but they have no real impact on the structure itself. Furthermore, there is now particular problem due to seismic loads which are very small in this region. The terrace has been retrofitted recently and no damage due to rain or other climatic events can be found. The building itself is rather healthy and safe. The main problem due the rehabilitation is the consequence of urbanistic and architectural choices. It has been decide to modify strongly the external and internal aspect of the building in order to create smaller housing units with 26 to 36 apartments with a strong social identity and a direct link to a specific urban area (street and backyard). In order to improve the overall quality of live of the inhabitants, all the entry halls and staircases will be redesigned and special spaces will be allocated to bikes parking and selective garbage treatment. All the networks (phone, television water and other fluids) will be distributed in technical shafts secured again fire propagation. 2.3 Actions From a structural point of view, the main challenge of this project is to create from a continuous and linear architecture, a sequential one by eliminating a part of the building and creating tree main arches through it. This is in fact planned while the building is still habited. Due to the prefabricated structure of the walls, this strong modification of the building cannot be done without designing an additional structure. Figure 6 presents the general layout of the rehabilitation project. The lower image presents the actual façade and the two upper ones represent the two new façades.
The Utrillo Building Rehabilitation Project
9
Figure 6: General presentation of the rehabilitation project.
The main problem in realizing the arches is that it needs to build a new structure able to support the loads due to the three upper levels without creating new solicitations or instabilities to the structure. Thus, the main problem is to solve the interface between the existing structure and the arches. In order to avoid any cracks or disorders, this structure will be build internally to the building. The deconstruction will take place only after the achievement of this structure. Figures 7 and 8 presents the existing structure and the integration of the arches.
Figure 7 : Existing structure
10
The Utrillo Building Rehabilitation Project
Figure 8: Integration of the arches in the existing structure.
2.4 Description of the works 2.4.1 Specific deconstruction problems 2.4.1.1 Walls The walls are supporting compression loads, thus it is not possible to deconstruct any walls without integrating a new structure. In order to create the arche, it is necessary to deconstruct on 11.5m wide on 5 levels without altering the stability of the 4 additional levels. 2.4.1.2 Ceiling The ceiling elements are working without any continuity from one to another. Their deconstruction does not create any particular stability problem. The pins assuring the link with the remaining walls will be maintain in order to avoid any weakness of the structure at these locations. 2.4.1.3 Technical shafts The technical shafts being completely independent of the overall structure, one special support will be created in order to maintain the existing ones in the 4 remaining levels. 2.4.2 Constructive solution for the arches In order to support the loads of the 4 remaining levels, it was proposed to ??? use 7 concrete porticos founded on 7 short concrete piles. The interface with the existing structure is made of a steel structure fixed by a controlled tightening of the walls under the last ceiling. The porticos will also be tightened to the walls. The use of a steel structure imposes to avoid any sliding between this structure and the walls. This is why a specific system using a reinforcement by carbon fibers and polyesters will be used.
The Utrillo Building Rehabilitation Project
Figure 9: Detail of the assembling between existing walls and the steel structure.
Figure 10 describes the positioning of the steel structure.
Figure 10: Section of the steel structure under the floor of level 6
11
12
The Utrillo Building Rehabilitation Project
Finally, the whole steel structure will be installed and supported by the concrete porticos as shown on figure 11.
Figure 11: Plane view of the steel structure.
Then the whole structure will be supported by 7 porticos in reinforced concrete. Figure 12 gives the repartition of the 7 porticos under the floor of level 6.
Figure 12: Position of the 7 porticos under the floor of level 6.
The Utrillo Building Rehabilitation Project
13
All the porticos are similar even if the one located at balcony level is more solicited. All are reinforced as this one. In order to maintain a good link between the walls and the piles of the porticos, a specific system using U steel embedded in the wall as detailed on figure 13.
Figure 13: Assembling between the piles of the porticos in reinforced concrete and the existing walls.
Figure14: Final view of the reinforced concrete porticos.
14
The Utrillo Building Rehabilitation Project
3 REFLEXIONS The project is now finished and the principal work is planned for the very next weeks. The urban refurbishment of the “Mireuil” District in La Rochelle can be considered as a good illustrative example of the French policy of improvement of social, architectural and environmental renovation projects of social housing.
Change of Identity of “Geldershoofd” in Amsterdam – Bijlmermeer L.G.W. Verhoef Faculty of Architecture, Delft University of Technology, The Netherlands.
M. van der Lubbe ANA Architects, Amsterdam
A. uit den Boogaard Ingenieursbureau Strakee, Amsterdam
ABSTRACT: The ‘Geldershoofd’ building was originally designed as a modular construction. It is fit only for the function for which it was initially intended. Because of the limited strength of the foundation no extra load can be carried. A proposal for strengthening will be shown. Possible measures to stabilize a part of the building after creating bigger openings in the building, such as those used for the ‘Hoge poorthuis’ are also considered. Finally, the solution for extending floors to the outside of the original facade with the aid of the existing cantilevered concrete beams will be described. The cantilevered concrete beams alone are not strong enough to carry the new floor load.
Fig.1a Multi storey residential blocks in “de Bijlmermeer”, Amsterdam
Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved
16
Fig.1b View of the original “Geldershoofd”
1 GENERAL DESCRIPTION OF THE CASE STUDY The “Geldershoofd building”, a multi storey residential block for 1300 people in 502 dwellings was built in 1965 as a part of the urban plan for Amsterdam-South East (Bijlmermeer). The urban plan was based on the CIAM (Congrès International d'Architecture Moderne) ideas. There were roads on the second level, from which cars could drive directly into the separate building that provided parking space for the cars of the residents of the ‘Geldershoofd’. This building was connected with the ‘Geldershoofd’ building by means of a covered bridge, so that people could walk to their homes without getting wet. The first level, the ground level, could be used by pedestrians and cyclists only. It was a green area with many plants, including bushes and trees. The buildings were hundreds of metres long and 10 or more storeys high. Initially the philosophy worked in practice, but as the bushes grew higher the paths between the buildings became increasingly narrow and dark and social control decreased. Moreover, the buildings formed a monotonous, massive block and were anonymous. Residents could not identify the own dwellings. The building system, with galleries on one side and balconies on the other side, made it impossible to see what was happening at ground level. It became dangerous to live there. Despite this the concept made this part of the town fascinating and exciting, especially to planners and architects. The contrasts between public and private areas, urban and rural landscapes, and collective and individual existed within this planning area. To upgrade Amsterdam-Bijlmermeer it became necessary to take a number of decisions. These included the demolition of a number of buildings of the ‘Geldershoofd’ type and their replacement by replaced by three storey detached houses, thus changing the monotonous image, and returning the road from the second level to ground level. The latter decision resulted in the loss of the urban ideal of separate infrastructure for cars and pedestrians. To tackle the social problems in the area it was necessary to improve the quality of space and social management.
Change of Identity of “Geldershoofd”in Amsterdam - Bijlmermeer
17
ANA architects (Marcel van der Lubbe) were commissioned to create a new image, by changing the identity of “Geldershoofd” in such a way that the upgraded building could harmonize with the new surrounding. The idea behind the plan for upgrading “Geldershoofd” was to create a number of different types of dwelling within the existing building. These new types would play a role in the obtaining the desired combination of various types of residents, bearing in mind the urban conditions and the potentials of the Bijlmer. The new dwelling types, in combination with a new infrastructure inside and outside the building, provide the setting for the new identity. The diversity of dwelling types reflects the diversity of residents. The results obtained are: diversity of residents, buyers or tenants, cheaper or more expensive rents. The image of the residential block is no longer monotonous and these interventions have improved the social security of the residents. The new types of dwelling were given appropriate names and include: kophuis (‘top-end’ apartment), hoge poorthuis (‘high archway’ apartment), loggiahuis (‘loggia’ apartment), (hofhuis (‘courtyard’ apartment), atriumhuis (atrium apartment), rij in huis (‘drive-in’ apartment), autolift huis (‘car lift’ apartment), etalage huis (‘shop-window’ apartment), erkerhuis (‘oriel window’ apartment) and terrashuis (terrace apartment). The project has not yet been implemented. 2 STRUCTURAL PROBLEMS 2.1 Typology of structures In Amsterdam, as in most of the western parts of the Netherlands, a deep foundation is necessary. Concrete piles were driven into the ground to reach the bearing sand layer at about twenty-one metres below ground level. The piles are located under the bearing concrete walls and perpendicular to the length direction of the housing block. On top of the piles a concrete beam was poured in one operation with the ground floor, which is resting on the earth. Next to it, special steel tunnel formwork was erected on the ground floor, as formwork for the side walls and the underside of the floor. At the same time, prefabricated cantilevered beams were placed at both ends of the tunnel formwork, with rebar’s projecting into the space between two tunnel formworks for the walls. The next step was to pour concrete between the formwork and on top of the deck to create the 2nd level, with bearing concrete walls underneath. The tunnel formwork was and is still standardized travelling formwork. Inside the tunnel the temperature was kept artificially high, so in a few days the tunnel could be removed to be used elsewhere. Materials such as concrete and more especially steel were expensive. With this in mind the spans of the floors were rather small. In the ‘Geldershoofd’ building the spans were alternated between 5 and 3 metres. With this design tool each dwelling had three load bearing walls; two of these were shared with the neighboring tenants and one was placed between. The walls were only 180 mm thick. The floor thickness, which was related to the biggest span of 5 metres, was 170 mm and was later covered with a 50 mm sand-cement layer. The total length of the building is 315 metres and it is sub-divided into 8 sections, each about 40 metres long and with its own stability system. Two types of dilatations are made between the different parts; four real dilatations where there are two bearing walls next to each other and four with a hidden dilatation on which the floors are resting on the other section.
18
Fig.2 Floorplan
2.2 Problems Due to the chosen typology and the measurements of the structural elements the system can be seen as a modular construction, only for the function as has been foreseen at the time the building was erected. The catering for the need for flexibility to accommodate future requirements was not an option. The foundation was calculated precisely. That meant that when two spans of 4 meters are supported on one bearing concrete wall more piles were driven into the ground than when two smaller spans were supported on a concrete wall. There is no extra capacity for future change. Each bearing wall has its own possibilities and limitations and wherever possible existing openings have to be used to open up walls. In some places and under some conditions it is possible too connect elements to the existing walls or to build up elements on top of the walls, but in other cases it is necessary to strengthen the foundation. The division of the building (see Fig. 2) into parts, each of which has its own stability system, creates a problem if bigger openings in the building are found necessary for a new use of the building. Bigger openings can influence the stability of the building. The cantilevered beams to carry the weight of a balcony or gallery slab, together with the weight of some people, are not strong enough if the function changes from balcony to floor. Walls and floors as designed too thin to provide adequate sound resistance. The thickness of walls is180 mm while the thickness of the floors is 170 mm concrete and 50 mm top of a sand cement layer. 2.3 Actions To achieve the desired change of identity it was necessary to make many types of dwellings. This paper describes some of the interventions. The strengthening of the foundations, together with the addition of dwellings at the top of one end of the building is described in 3.1‘Kophuis’. The creation of bigger openings and the means to maintain the stability of the structural system is described in 3.2 ‘Hoge poorthuis’ and finally, despite their limited strength, the use of cantilevered beams will be described under 3.2 ‘Etalagehuis’.
Change of Identity of “Geldershoofd”in Amsterdam - Bijlmermeer
Fig.3a Position ‘kophuis’ in ‘Geldersepoort’
19
Fig.3b View of ‘kophuis’
3 DESCRIPTION OF WORKS 3.1 ‘Kophuis’ The ‘Kophuis’ distinctly differs from other buildings in the surrounding area and is important to the provision of a new identity of Geldershoofd by changing the anonymous honeycomb structure of the Bijlmer. This ‘ kophuis’ part of the ‘Geldershoofd’ building is designed for elderly people who desire greater luxury. The apartments are opened up by means of short galleries that can also be used as places to sit or to meet others. In the dwellings of the ‘kophuis’ afford views in three directions. The addition of the ‘Kophuis’ to the existing building means that the end bearing wall has to carry a greater load. Although the concrete wall itself is strong enough, the foundation is not so extra piles have to be driven next to the existing piles. The easiest way to provide the necessary addition strengthening is to add ‘renovation piles’. Holes of ø 80 mm will be drilled through the existing concrete foundation beam. Through these holes sections of the foundation piles are screwed into the ground until the bearing sand layer is reached at a depth of 21 metres below ground level. The piles are drilled into the ground under a slope of about 1:5. Two such piles can carry about 300 kN. In total 4 renovation piles are necessary for strengthening. The three storeys that have to be added to the existing concrete structure of the ‘Gelderse hoofd’ are executed as a steel truss cantilevered over the roof, while the two floors beneath are suspended from on this truss. For a statically ideal scheme for the truss see Fig 6. However the positioning of such a truss is a source of conflict because people have to pass easily without noticing the bearing structure. For this reason an adaptation has been made to provide a structure that consists of a of a combination of a truss and a Vierendeel truss (see Fig 7).
20
Fig.4a Top floor ‘kophuis’
Fig.4b Suspended floor ‘kophuis’
Fig 5 Drilling renovation piles through the existing structure
Change of Identity of “Geldershoofd”in Amsterdam - Bijlmermeer
Fig.6 Statiscally ideal scheme for spants 1 & 2
Fig.7 Conflict (upper drawing) & Statisch schema spant 1 (lower drawing)
21
22
3.2 ‘Hoge poorthuis’ The ’Hoge poorthuis’ is situated over the original entrances to the long building. These entrances had a structural height of one storey, but in reality were lower because of pipes that were concealed by a false ceiling. The width of the entrance lobbies was two bays. These were dark places without ‘social eyes’ in the surrounding area to see what was happening, so it was dangerous at night. Now the entrances have to be only one bay wide but 5 storeys high. Dwellings are split, being separated by the five story high space but with their two separate parts connected by semitransparent corridors. The corridor is within the field of vision of the tenants. To open the passageway up to five storeys high, it is necessary to remove the second to the fifth floors. These floors were necessary for stability reasons in the length direction of the building. Without the floors there is a real chance of collapse.
Fig.8a Position ’Hoge Poorthuis’, in ’Gelderse poort’
Fig.8b Vertical section through ‘Hoge Poorthuis’
To prevent instability, parts of the floors will remain in position during the execution of the strengthening work. A steel structure will be built against the last concrete wall of the stiff core (on line37, Fig 10) and connected to it. For the dimensions of the columns and beams a profile of HE220 A has been chosen. Between this steel structure and the disconnected concrete wall (on line 38, Fig 10) there are four horizontal beams on the third and fourth floors; two carrying the semi-transparent corridor and two freely visible in the space of the ‘Hoge poorthuis’. After the horizontal connections have been positioned and connected, the rest of the concrete floors can be removed and the steel structure covered by a layer of insulation and plating.
Change of Identity of “Geldershoofd”in Amsterdam - Bijlmermeer
23
Fig.9 Removing floors can cause instability
Fig.10 Strengthening of wall 37 with a steel structure
3.3 ‘Etalagehuis’ The distance of this part of the building from the opposite neighbours is 350 metres, which means that privacy is guaranteed. By designing maisonettes, by adding the balcony areas to the dwellings, which are then covered by a transparent facade, a vacant space from which both parts of the dwelling can be experienced is created. In this part of the building, which has been changed to create an ‘etalagehuis’, the maximum spatial quality has been reached by minimal changes to the dimensions.
24
Fig.11a Position of ‘etalagehuis’ in ‘Gelderse poort’
Fig.11b View of the facade of the ‘etalagehuis’; the surrounding preexisting structure remains
Of course the prefab concrete balcony elements have to be removed. The cantilevered beams on which a column was suspended to connect the concrete balustrade have to be changed. It is also necessary to remove the columns, with exception of those at each end of the ‘Etalagehuis’. The existing floor area must be increased to span the space between the cantilevered beams. As is the case throughout the building, the total thickness of the floor will be 170 mm concrete, plus a 50 mm sand-cement layer for levelling. The service load remains 1.5 kN/m2. Altogether this is a bit more than was calculated, which means either accepting a lower safety factor, which is not a real option, or keeping the cantilevered beam in place and thus visible in the vacant space. If both the cantilevered beams are connected to each other they are strong enough to carry the extra load. However, if the tenant or buyer does not wish to see the cantilevered beam in
the open space, the option is to roughen up the top level of the cantilevered beam by grit blasting, to drill holes in the top of this beam and to place chemical bonded anchors in these holes so that the beam and floor work as a T-shaped beam which is higher and stronger than the cantilevered beam alone.
Change of Identity of “Geldershoofd”in Amsterdam - Bijlmermeer
25
4 CONCLUSION
The change of ‘Geldershoofd’ shows how multi storey residential blocks can be changed in different ways to reach a new identity. To ensure that the apartments are ‘fit for purpose’ changes are necessary because in the meantime insulation requirements have increased time and ‘monoculture is also no longer an acceptable option for residential buildings. To make new divisions and distinctions is especially important because the owner or tenant can then more easily recognize his own apartment from the outside. The individual dwelling can be identified and becomes a place to be proud of. This is the main reason to change the identity of multi storey residential blocks and at the same time to extend the economic life of these types of blocks. REFERENCES [1] Lubbe, M van der, Geweldig huis, 2001 [2] Stigt J. van, Verhoef L.G.W., Renovation and Maintenance techniques. Lecture book, Delft University of Technology, 1998 [3] Verhoeks, M.M., Schut-Baak P.A., Rongen C.Th.H., Schuur A, Thijssen C.F.F & Verhoef L.G.W., Architectonische en Technische waardering van bestaande galerijflats, publicatieburo Bouwkunde, Delft, 1995
This page intentionally left blank
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence Roberto Di Giulio Department. of Architecture, University of Ferrara, Italy
Silvia Brunoro Department. of Architecture, University of Ferrara, Italy
Paolo Civiero Department of Architecture ITACA, University of Rome “La Sapienza”, Italy
ABSTRACT: This paper presents the structural adaptation of the residential buildings “Le Navi” in Florence. As well as tackling the typological, architectural and environmental obsolescence of the multi-storey blocks, the refurbishment programme also achieved compliance with current national seismic regulations. The intervention on the structures involved above all the introduction of tension rods for wind bracing, that improve and reinforce the structure in relation to seismic events.
1 GENERAL DESCRIPTION OF THE CASE STUDY The “Le Piagge” District in the Municipality of Florence is the location of a residential complex, called “Le Navi” as it is shaped like a ship, built at the end of the 70s for renting to lowincome users (Fig. 1).
Figure 1. Urban district Le Piagge, Florence
This project was carried out with the support of the recent Italian law on urban renewal called “Contratti di quartiere” (“Neighbourhood Contracts”, Ministerial Decree 22.10.1997), which mainly focuses on the regeneration of town districts severely affected by social, economic and physical decay. It points out the fundamental role of the rehabilitation of existing housing estates, rather than that of overall renewal. The renewal plan was carried out using public funding from three different programmes: the “Neighbourhood Contracts”, the “Urban Recovery ProImproving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
28
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence
gramme”, and the “Experimental Building Programme”, the co-ordination of which involved significant efforts in terms of engineering. These programmes are aimed at the urban and environmental recovery of the whole district. They contribute to the social and economic development of the area through the direct involvement of users in the development of the programme. The intervention was particularly devised to solve four main factors of building deterioration: The inadequacy of residential typologies in relation to the distribution of families and the needs expressed by users; The overall presence of severe building pathologies due to the use of unsuitable/poor-quality materials and construction technologies; The poor quality and/or poor performance of building services in relation to the distribution of the buildings (the “central atrium” type with duplex housing on two sides inevitably leads to a negative effect on the internal quality of the units. These negative effects involve air flow, lack of transverse ventilation, presence of humidity in the rooms, etc.) The lack of solutions that could give the various parts of the site an architectural identity and reduce the alienating character caused by the repetitiveness and anonymity of the buildings. Many of the interventions involve both the structure and the envelope, and are aimed at the typological, technological and structural rehabilitation of two of these three identical buildings, each with 140 living units. Redevelopment of the overall site area, of about 55,000 square metres, is also planned. The project includes the creation of a public garden of high environmental quality with forest areas and small hills to break up the flatness of the landscape and create more interesting pedestrian and cycling areas. 2 PROBLEMS CONCERNING THE STRUCTURE 2.1 Type of structures (referred to the aspect analysed) The structure of the buildings is formed of parallel reinforced concrete walls cast in situ at a modular distance of 6.8 m, thus forming a structural frame which strip windows and prefabricated panels and floors are inserted into. Consequently, the type of dwelling is characterized by the repetition of a module corresponding to the constant distance between the structural walls. (Fig 2-3)
Figure 2-3. The structure formed by parallel concrete walls is visible in the modularity of the façade
2.2 Problems Structural problems particularly concern the inadequacy of the structure for seismic loads. The structure showed a widespread presence of defects resulting from the deterioration of the materials and the unsuitably rigid construction technologies used. Furthermore, as regards the enve-
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence
29
lope there are a lot of problems which are strictly related to the structure of the building and the interventions required, such as the lack of insulation of façades and roofs, the decay caused by pelting rain and the action of mould, and the lack of liveable areas and small balconies. (Fig. 4-5)
Figure 4-5. Decay of the façades due to atmospheric agents
2.3 Strategy for improvements This project provides an answer for structural, architectural and technological problems by concentrating efforts on four main tasks: - Modifying the distribution of residential types and optimizing the planning of the units with the aim of making them respond to the needs expressed by users; - Highlighting the maintenance, renovation and replacement interventions necessary to eliminate the effects and causes of the decay, to comply with standards and, more generally, to improve living conditions; - Improving structural performance; - Introducing, as far as restoration of the facades is concerned, architectural elements that can reinforce the architectural identity of the two buildings. Diversification of the façade solutions will create a less alienating and more familiar urban landscape. Furthermore, the aim is to improve the living quality of the units by looking at the architectural elements and the aspects that guarantee building hygiene. In particular, the living quality of the connecting spaces between the two buildings has been enhanced by the addition of courtyards in the middle of the horizontal circulation of the units. The courtyards interrupt the internal walking path, thus providing natural light and air circulation for the buildings. As well as improving the environmental quality of these spaces, such a solution significantly reduces the negative effects of the presence of long, dark corridors. The refurbishment strategies, which include both structure and envelope, were aimed at developing the following objectives: Compliance with seismic regulations; Complete renovation of the façades with the overlap of a thermal insulation layer (external thermal insulation coating); Replacement of external windows and doors to improve their thermal insulation properties (this also contributes to enriching and bringing character to the external façades); Complete replacement of the balustrades of the existing balconies with diversified solutions including: galvanized steel balustrades with a solid lower part, and balustrades in a light, transparent material; Creating new balconies overhanging the level of the duplex units with galvanized steel balustrades and coloured safety glass; Finishing the balconies at the top two levels with a galvanized steel grill and added balustrades. The balustrades are made from coloured safety glass and galvanized steel grill panels;
30
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence
Partial enclosure of the balconies near the new heating units (boilers) with galvanized steel panels (inserted using the “dry method” in accordance with prefabrication techniques); Addition of internal courtyards that interrupt the long (internal) layout corridors and allow natural light and air flow (improvement of environmental conditions). Compliance with current standards regarding hygiene (sanitary facilities) and utilities (electrical systems); Setting up a powered ventilation and recirculation system for improved air displacement in the single-sided units. 2.4 Actions The main actions involving structural interventions can be listed as: - Reinforcement of the concrete structure via a hardening intervention with the introduction of tension rods for wind bracing between all structural modules; - Addition of new balconies made from a 3 m overhanging concrete slab, galvanized steel and coloured safety glass. The guidelines for design management particularly focussed on avoiding large-scale, intrusive or destructive interventions on existing structures, and also included: - a careful and detailed reconnaissance of the existing structures, their layout, nature and primitive character; - identification of technical resources and strengths, and their disposition. Factors which influence the behaviour of the entire structure were identified and evaluated in accordance with the terms established by the regulations in force, in particular: L. 2/2/1974, no. 64 L. 26/4/1976, no. 176 L. 25/11/1982, no. 1684 D.M.LL.PP. 14/2/1992 D.M.LL.PP. 16/1/1996 Circ.Min.LL.PP.10/4/1997, no.65/AA.GG. CNR 10011/88 The occasion of the functional and structural refurbishment of the two buildings, divided into two identical units both in terms of geometric shape and design solutions, provides the opportunity for the seismic adaptation of the existing structures, to develop comparison models and therefore to test solutions and devices related to connections. Through the use of a mathematical model, more proposals have been made for possible interventions highlighting successes and/or failures, which will be illustrated in section 3. (Fig. 6,7).
Figure 6 Dynamic deformations. Longitudinal seismic effects
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence
31
Figure 7 Dynamic deformations. Transverse seismic effects
2.5 Description of works and critical evaluation 2.5.1 Structural upgrading After checking the different configurations caused by seismic action, it was decided to use a cell by cell hardening intervention between each structural module, which also included the addition of wind bracing tension rods to improve and reinforce the structure in relation to the seismic event. The elements forming the new structure are: - Steel diagonals: Fe430B steel profiles, tubular section, ij 101.6 mm, thickness 5.6 mm, painted with rust inhibitor, joined to metal plates; - Metal plates for anchoring the hardening diagonals: thickness 20 mm, dimensions 220x800 mm, directly fixed and glued to the structure at each floor; - Flexural connections of the joint made from steel bars Fe B44 K (Fig. 7-9), thickness 16 mm, dimensions 150 mm. These are inserted into 60/50 holes at the bottom of the structural walls, protected by plastic membranes and filled with expansive mortar EMACO 2000 kg/m2 concrete.
Figure 8 Wind bracing tension rod scheme
32
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence
Figure 9 Detail of the wind bracing tension rods. Longitudinal section
Figure 10 Detail of the wind bracing tension rod. Cross-section
The distribution of the strengthening profiles was, of course, carried out in relation to the distributional and functional requirements of the building in its final prospective study, but also in such a way as to control the increases in stress in a compatible way, specifically and locally reconsidered in the structures already in place (Fig. 11-16). Because of the remarkable monolithic nature of the structure, it was also difficult to design accurate means for noise insulation. For this reason, the use of specific technical solutions in the structural joints that can help in the interruption of various kinds of vibration waves was tested.
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence
Figure 11 Hardening near the installations Figure 12 The cavities near the new structures
Figure 13 Welding between tubular profiles Figure 14 Top steel plate for anchoring
Figure 15 Bottom steel plate for anchoring Figure 16 Anchoring operations to the existing floor
33
34
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence
The main interventions for interrupting vibration waves were the following: Use of an adhesive polymer film at the interface between existing floor and the new rough floor (including one vertical strip at the position of the vertical panels) to interrupt the material continuity of the elastic medium, with a view to improving vibration insulation while still maintaining the expected mechanical efficiency of the structural reinforcement; Use of reinforced neoprene cushions alongside the anchoring plates for the wind bracing profiles in order to increase knowledge of and obtain quantitative comparisons for the effects of introducing structural reinforcements (concrete reinforcing, steel diagonals) on the sensitivity of the material and continuity connections in the structure for noise transmission. Particular attention was also paid to noise produced by the system networks concentrated in the cavities beside the new structures. The mathematic model used allows new intervention solutions to be proposed, highlighting successful results and/or failures. It was decided to give less importance to the stair units as the quality of their foundations, being clearly in a condition of weakness, did not match their strength and aseismic capacity. Generalised cell by cell reinforcement was used to unload the units, rebalancing their role and function (these units were not conceived of, designed and/or constructed as priority earthquake defences). Within this framework, the structural and heatproof joints (except those on the top floors) were removed, eliminating the differences in resources and rigidity and producing a sort of “uniform strength”. The structure is affected by a variety of smaller interventions at a local level caused by the new distributions. These do not, however, alter general performance expectations. Rather they confirm the regularity and symmetry, contributing to achieving predictable behaviour without any unusual escapes or unexpected stress “peaks”. 2.5.2 Upgrading façades and adding balconies. Interventions for refurbishment of the facades included the following actions: - Removal of the existing windows, changing type, geometry and distribution of the openings, assembly of new aluminium window frames; - Creation of an external thermal insulation system (ETICS) and, in the structural walls, creation of a cavity for the insertion of the pipes for the new boilers; - Removal of all of the parapets of the balconies and their replacement with new parapets in concrete and galvanized steel; - Creation, on the second floor, of new balconies with a concrete slab overhanging by approximately 3 metres and parapets made from galvanized steel and coloured safety glass; - Creation at the position of the balconies on the top floor of a galvanized steel structure which vertical and horizontal opaque grill panels and coloured safety glass panels as parapets are inserted into; - Creation on the top balconies of horizontal grill elements in galvanized steel with functions of solar shading.
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence
35
3 TECHNICAL DATA SHEET The structure was checked through the assessment of loads and overloads in compliance with Ministerial Decree 16 January 1996 and using the following seismic parameters: Table 1. Seismic parameters used. _________________________________________ Seismic coefficient 9 Seismic protection coefficient 1 Foundation coefficient 1 Coefficient of response 1 Coefficient of structure 1.4 __________________________________________
The calculation of loads and overloads for verification was in compliance with the aforementioned Ministerial Decree 16 January 2006, particularly considering: - Living volume: accidental overload equal to 200 kg/m2 with inertial rate of 0.33. - Balconies: accidental overload equal to 400 kg/ m2 with inertial rate of 0.33. - Roof: accidental overload caused by snow with inertial rate of 0.33 equal to: qs = ȝ1 qsk where: qsk = 115 kg/m2 (zone II, to s < 200 above sea level) ȝ1 = 0,8 (stratum angle < 30°)? qs = 92 ~ 100 kg/ m2 The model for analysing the entire building was created by modelling all of the reinforced concrete walls using shell elements with a thickness of 18 cm. The need to model the bracing system prevented the use of a rigid floor outline. The problem was resolved by modelling several floor levels with shell elements with a thickness of 28 cm having no density in order not to load the bracing elements that would only be activated following a seismic load. In fact, these elements are installed by connecting the various already deformed floors. The floor load is thus transferred onto the main walls (and on the beams of the corridor) as a distributed load in accordance with the calculations given below. The procedure involves dynamic analysis in two distinct stages: the first calculates the frequencies of the vibration itself, the second calculates shifts and stresses resulting from the response spectrum assigned in input. From the point of view of processing time, the stage of frequency calculations is more burdensome: this stage was kept separate, however, to the stage of calculating the spectral response and is always launched first. There are two specific printing phases for these results, one which involves the oscillation frequencies only and a second which also highlights eigenvectors. Thus, once the frequencies have been identified, if the system to be resolved does not change, the user can then proceed with spectral analysis only. In the spectral analysis, the program (MASTER SAP) uses the response spectrum assigned in input, as set out by the regulations. For the global directions X and Y the spectrum decreases for periods of more than 0.8 seconds. The spectrum in the global direction Z, if present, is unitary. The amplitude of the spectrums of responses is determined by the seismic parameters foreseen by regulations and assigned in input by the user. The procedure initially calculates the modal participation coefficients for each direction and frequency of the seismic event. These coefficients can be seen as the dynamic contribution of each mode of vibration in the assigned directions. It will therefore be possible to see which direction each individual mode of vibration has predominant effects in. Subsequently, the shifts and stresses for each dynamic direction activated are calculated for each mode of vibration. The overall effect, caused by the individual modes of vibration, is calculated for every dynamic direction by means of the square root of the sum of the squares of the individual effects. A specific printing stage is foreseen for these results.
36
Techniques for Adaptation of the Structures of a Multi-storey Family House in Florence
The last processing involves calculation of the total effects, obtained by taking into consideration all of the dynamic directions applied. These results (envelope) can be obtained, at the user’s discretion, in three separate ways, including those suggested by Italian regulations and by the Eurocode 8. 4 CONCLUSIONS The urban refurbishment of the district “Le Piagge” can be considered as one of the most representative interventions in terms of improvement of architectural, technological and structural performance. The final design, involves an overall investment of 17 million Euros, with a net building cost of 13.5 million Euros, 3.2 of which were spent on the building envelope. The purpose of the work is to obtain 312 newly refurbished units by improving the quality of the 280 existing ones and designing 32 additional ones of a smaller size. Hence, the cost of each unit is about 43,500.00 Euros, 10,300.00 Euros of which were spent on the building envelope. The sum of all the unit areas is 25,600 square metres. The cost forecast is therefore 530 Euros per square metre, 125 Euros of which were spent on the building envelope. 5 REFERENCES AA.VV. 1986. Tra cronaca e storia: contributi critici e realtà operativa. Roma: IACP Ginelli, E. 2002. Tecnologia, progetto, manutenzione. Milano: Franco Angeli AA.VV. 2004. L’intervento sul costruito: problemi e orientamenti. Milano: Franco Angeli AA.VV. 2005. Abitare il futuro: Città, quartieri, case. Bologna: BE-MA
A Future for WBS 70 The Franz-Stenzer Building Block as a Case Study W.J. Quist Faculty of Architecture, Delft University of Technology, The Netherlands
ABSTRACT: In the post war construction until the fall of the wall in 1990, about 3 million residential units were built in the former GDR. 27,5 % was constructed using the WBS 70 large panel system. Over one third of the post war building stock is situated in large urban areas like Marzahn (Berlin). Marzahn was built from 1978 on-wards and created almost from scratch until it reached 62.000 housing units shortly after 1990. A redesign has been made for a large building block containing 580 dwellings, situated near the commercial center of Marzahn. The redesign consists of an urban relocation of functions and an adapted traffic plan, but also the complete interior redesign as well as a totally new façade. The interventions are designed as a catalog to be used in transformations of other WBS 70 building blocks.
1 INTRODUCTION In 2002 the project was started (Quist 2002) at the Delft University of Technology and it was finished in December 2003. The project is aimed at two main targets, one in the field of Architecture, one in the field of Building Technology: - To make a redesign for a WBS 70 residential building of eleven stories in such a way that the diversity of floor plans increases. The ultimate goal is to make a combination of dwellings, suitable for all ages and all sections of the population. - To define the possibilities and impossibilities of the building system WBS 70. The ultimate goal is to control and strengthen the architectural design. The project is a continuation of a graduation research by Jos van Buuren, focused on the possibilities of urban renewal of Marzahn (Van Buuren 2001). 1.1 General facts The new federal states (former GDR) have approx. 3 million post-war dwellings. 33% of this building stock is situated in large residential quarters with more than 2500 dwellings (Ott 1997). From the seventies onwards those residential units are created within tenement houses made of large prefabricated concrete panels. After die Wende (the fall of the wall) big social problems arose within these residential quarters. Nowadays 1.3 million housing units are unoccupied. Within the area of Marzahn, some housing blocks are unoccupied for over 20%. 1.2 Marzahn Marzahn is one of the biggest plattenbausiedlungen (urban quarters with large concrete panel buildings) in Germany. It consists of 62.000 housing units and was built between 1975 and 1991. There is a very high housing density, but there are also a lot of green areas. Most of the Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
38
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
housing units were constructed using the WBS 70 building system (45% for 11 stories and 26% for 5/6 stories), but also QP 71-10 (16%) and WHH 18/21 (13%) were used. The residential area is an urban area in itself (maximum 180.000 inhabitants), but due to its situation within 20 km of the center of Berlin it does have really metropolitan possibilities. The city center is reachable within 20 minutes by public transportation and the airports Tegel and Tempelhof are within 45 minutes by public transportation.
Figure 1. Typical WBS 70 elevations.
1.3 WBS 70 The building system WBS 70 was developed during the late sixties and seventies by the Bauakademie der DDR – Institut für Wohnungs- und Gesellschaftsbau. The development resulted in 1975 into building regulations, which had to be followed by architects and building contractors. The system is a fully integrated building system; it contains bearing elements, façade elements, internal finishing, staircases, bathrooms, etc. Within 18 years about 650.000 housing units were built using the WBS 70 system (www.wowi.de). The construction time for one team was around 4.5 dwellings per day. One can also find the WBS 70 buildings (or variations) in other Eastern European countries like Poland, USSR, Hungary and Czech Republic among others. The buildings are recognized by their rigid pattern of heavy weight concrete loggias on one side (Fig 1) and by the flat and boring representation of the other side. The WBS 70 building block does have two main representations; one is constructed in a curve of approx. 450 m, embracing a green inner court, the other construction type is a rectangular building block of approx. 100 m length. Figure 2 shows a typical floor of a WBS 70 building with three housing units arranged around a hallway, which contains a staircase, an elevator and a garbage shoot. Recognizable are the wide loggias (span: 6 m) and the uniform, prefabricated bathrooms. Figure 3 shows the building construction in general. Large prefabricated concrete panels are placed on top of each other. The reinforcement is welded together to create a stiff and stable construction. The span of the floors is 6 m and the maximum weight of each panel is 63 kN.
Figure 2. Typical WBS 70 floor plan.
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
39
Figure 3. Isometric view of the WBS 70 construction
2 FRANZ-STENZER BUILDING BLOCK In 2000-2001 the Franz-Stenzer building block has been renovated, therefore this paper is purely academic. The starting point will be the building block before renovation. 2.1 Urban situation The Franz-Stenzer building block is situated near de commercial and cultural center of Marzahn. Also different types of schools are in the neighborhood. The building block itself is constructed in a curve around two other building blocks (6 floors) and a private football field (Fig 4). The different sections of the building contain different amounts of housing units. Table 1 shows the division of the housing units. It’s clearly visible that most of the dwellings contain 3 rooms, equivalent to 68 m² of net floor space.
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
40
Figure 4. Scheme of the FS building block and the immediate surroundings. Table 1. Number of housing units in the FS building block
Section 1 2 3 4 5 6 7 8 TOTAL
1 18 3 18 6 2 20 4 20 91
Number of rooms 2 3 4 4 22 3 41 21 4 22 1 62 30 1 30 25 4 22 65 30 4 22 17 286 110
5 17 19 18 20 74
TOTAL 64 65 64 98 58 64 99 66 578
2.2 Architecture The architecture of the Franz-Stenzer building is just like all the other WBS 70 buildings. Figure 5 shows the façades. Clearly visible are the loggias, eleven floors above each other. This gives the building a vertical orientation. The building is limited by some kind of cornice of 1.5 m. Figure 6 shows the minimal entrances, repeating every 24 m. Just like all other buildings in the surroundings; the materials are mainly concrete with some additional steel, wood and plastic. The only buildings-specific item is the small breakthrough on ground level, measuring 6x3 m.
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
41
Figure 5. Elevations
Figure 6. Entrances (left: backside, right: front side)
3 PROBLEMS First of all the overall image of post war urban areas in the new federal states is very negative. Until the nineties, under the communistic regime, the plattenbausiedlungen did function very well because of the fact that there were no other housing units available. Besides that, there was a huge social cohesion within those urban areas on every scale. After the fall of the wall in 1989 the social cohesion broke apart; people went to western Germany, private house ownership was promoted, etc. But overall, there was a total aversion against everything that was left over from the communistic age; this includes the plattenbausiedlungen such as Marzahn. The downward movement of people with high (average) incomes leaving to other parts of the country hasn’t stopped yet. Problems in the urban area concern also the increased number of cars, increasing unemployment, small shops that can’t stand against large supermarkets, etc.
42
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
Not only social problems control the future of Marzahn, also the visible materials (mostly concrete and asphalt) in and around the building blocks do have a negative influence on the quality of living in urban areas like Marzahn. 4 GENERAL POSSIBILITIES The Franz-Stenzer building block in Marzahn is just an example and can be replaced by many others. In this chapter some general ideas about how to cope with plattenbausiedlungen built with the WBS-70 system are formulated. 4.1 Possibilities on urban scale About 75% of all the WBS-70 plattenbausiedlungen have one thing in common: All the sites are constructed within 30 minutes travel of a city centre, they are well connected by public transportation and the connections for long-distance traveling are pretty good. This ax radius of 30 minutes is widely accepted as a desirable distance for all city functions used by metropolitan people. This fact gives good conditions to develop the plattenbausiedlungen aimed at Young Urban Professionals. In terms of urban scale, not only the highest (city) level gives good conditions for redevelopment. Also the urban planning of the plattenbausiedlungen itself is very good and flexible enough to redevelop due to the wide and spacious subdivision of the urban area. On the level of building blocks, the WBS-70 buildings have the tendency to show a front façade and a back façade. This can be exploited to divided the urban space into a private part and a public part. 4.2 Architectonic possibilities The most negative characteristic of WBS-70 buildings is their rigid and boring external representation. A research has been done to discover whether it’s possible to change this representation. The research was aimed at 5 points: - The possibilities to add building parts to the façade (balconies, winter gardens, galleries, etc.) - The possibilities to extend the use of the roof of the building blocks. - The possibilities of creating breakthroughs in the building - The possibilities of changing the entrances - The possibilities of adding a new façade - Horizontal extension of the building Figure 7 and 8 show two different principles to horizontally extend a building. The first principle is meant to be a lightweight steel construction. A construction like this can be connected to the WBS-70 construction by steel consoles and bonded anchors. With this construction method it’s possible to make winter gardens, balconies and galleries with a maximum with of 2 m. Figure 8 shows the second principle. This principle is aimed at making heavy weight extensions. This construction method makes use of the concrete walls and floors of the WBS-70 system to transfer the load to the foundation. When one floor is extend over 3 m., about 15 bonded anchors in the upper floor are necessary to transfer the load to the existing construction (Verhoef 1999, Hordijk 1999)
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
Figure 7. Steel construction for four winter gardens
43
Figure 8. Principle of a concrete extension
4.3 Extend the use of the roof To change the monotonous volume of the building it could be desirable to ad some constructions on the roof of the building. One can think of the LOFTCUBE (Aisslinger) or a more traditional way of creating dwellings on top of the building. Calculations show that it is possible to add at least two heavyweight floors. 4.4 Making breakthroughs Removing parts instead of adding building parts can also change the monotonous volume of the building. Calculations have been aimed at removing 3.5 layers at ground floor level. It is possible to remove the bearing walls and replace them by reinforce concrete beams and columns. Figure 10 shows the construction method. The reinforced concrete beam should be well connected to the bearing wall above it. By doing this, the construction height of the beam can be reduced.
Figure 9. Construction principle for making a breakthrough
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
44
4.5 Changing the entrances One of the shortcomings of the WBS-70 building system is the invisibility of the entrances. Not only the visibility is a problem, also the size. Therefore the research was aimed at investigating the possibilities of removing (parts of) the bearing façade (see fig 10). The complete removal of façade elements is a complex operation because the elements are load bearing. When removing an element, cautious planning of a temporarily construction is necessary (Fig 10a). When an alternative load bearing construction is in place, the element can be removed. Also the surrounding façade elements must be partly demolished to create space for the construction of a porch that will replace the load bearing function of the removed element. As can be seen in Figure 10b it is impossible to create door openings at the floor above the intervention because of the porch-construction.
Figure 10a. Structural consequences of removing bearing façade elements
Vertical - original
Horizontal- original
Vertical - target
Vertical - execution
Horizontal- target
Horizontal-execution
Figure 10b. Removing bearing façade elements (horizontal and vertical sections)
4.6 Interventions in the façade Not only the entrances can be upgraded by structural interventions, also the facades of housing units can be made more useful and visually attractive by removing (parts of) the load bearing elements. In Quist (2003) the varieties (Fig 11) have been worked out in detail. A catalog has
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
45
been designed which offers different solutions for different needs. The removal of the parapet wall which creates the possibilities to introduce a balcony with easy access by sliding glass doors is the easiest to execute. Option 5 (Fig 11) is comparable with the intervention described in paragraph 4.5 with one exception: this could be the 8th floor, including all problems of creating a temporarily construction.
Figure 11. Execution varieties of breakthroughs in load bearing facade elements. 1. Existing 2. Easiest option, removing parapet 3. Removing parapet and “beam” 4. Removing “columns” 5. Removing complete element
4.7 Adding a new façade In the past an investigation was carried out by IEMB (www.iemb.de) to find out whether it’s possible to apply a new façade construction to the existing façade. It carried out to be possible to apply a new cladding up to 200 kg/m². 4.8 Internal possibilities As discussed in chapter 2 and 3 the problems of WBS-70 residential building blocks not only concern the facade. When renovating such a building it is necessary to introduce new apartment types to offer a greater variety and enlarge therefore the attractiveness of the building. New floor plans can be introduced by easily remove all the infill of the existing apartments, but this is no solution for over 50% of the housing units (see Table 1) because of a lack of square meters. Two housing units can be combined by (partly) removing load bearing common wall. The techniques are comparable with interventions in the façade. A second possibility is to create maisonnettes by (partly) removing floor elements (see Fig 12). This technical intervention offers architectonic possibilities to create double high spaces and it offers differentiation in the façade. Also sound problems can be reduces by vertically combining housing units.
Figure 12. Removing (parts of) floor elements.
46
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
5 REDESIGN FOR THE FRANZ-STENZER BUILDING BLOCK 5.1 Urban interventions As stated before, the possible positive future for the building block lies within the urban situation. The building block is situated right next to the main shopping promenade and the cultural center of Marzahn. Also schools, parking space and recreation space is nearby. To be able to fully optimize the urban routes, it’s necessary to create breakthroughs in the building block (Fig 12). The first intervention is meant to enlarge the existing breakthrough to make it more visible from a distance and lighter. The second large intervention is the most important one; it’s the connecting route to the Marzahner promenade. Together with a change of footpaths and cycle tracks this becomes one of the eye-catchers of the building block. The porch will also be used as an entrance. The third breakthrough is created in the northern section of the building block. Its goal is to connect the inner courtyard with the car park. Here it’s not the visibility that’s most important but more the actual connection of the two spaces (more horizontal orientated than vertical).
Figure 13. Interventions on ground level
Besides the breakthroughs, also the inner courts and the cross section should be changed to fulfill future needs. Figure 14 shows the current situation: a huge building (35 m high) with a tiny footpath just two meters away. This intimidating and almost scarry situation should be changed to the situation shown in Figure 16. The public footpath on the backside of the building has been moved for about 15 m. This allows private gardens to be made in de zone in-between. In
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
47
this way, a human scale is introduced. Figure 15 also shows the improvement of the facades by adding new balconies and winter gardens.
Figure 14. Original cross section
Figure 15. Desired cross section
5.2 Architectonic interventions Two problems have to be solved within the building block, first the facades need to be redesigned, and second the arrangement of individual housing units has to be rearranged. Rearranging the housing units will also involve the creation of new floor plans. Before starting to make a redesign for the facades, some starting points have been formulated: - Keeping the original shape of the building. The shape defines the inner court and makes the building “stand”. - Making breakthroughs on ground level (see paragraph 5.1) - Introduce architectonic new rhythms in the façade besides the 6 x 2,8 m rhythm of the existing construction. - Remove all the existing balconies because of their poor technical state and clumsy dimensions. - Create new balconies and a gallery above the large southern breakthrough. (Fig 16) - Point out the entrances (every 24 m) - Use modern, tectonic, human and durable materials in contrast to the existing concrete.
Figure 16. Sketches of a winter garden and a balcony
48
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
Regarding de floor plans could the following be stated: - The current housing units are to small to solve the 21st century needs. The average unit counts 68 m². This should be increased to 100 m². - The housing units should be able to accommodate several types of households from different layers of the population. - Specific target will be high-income elderly, DINK’s (Double Income No Kids), small families. - Combining housing units in a vertical way should create diversity in the housing stock. - Create double (or triple) high entrances and hallways. - The bathrooms should be updated Figure 17 shows some possible new floor plans to meet the 21st century needs. In Quist (2003) a lot of new apartment types have been introduces to compose a “new” building in an old skeleton. Combined with a new façade, the introduction of balconies on both sides of the building and a few larger elements to break the building visually apart, the building has become a new and modern identity (Fig 18, 19, 20).
Figure 17. New floor plans
Figure 18. Front facade
Figure 19. Rear facade
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
49
Figure 20. Impression of the gallery, indicating the use of materials and their dimensions.
6 FEASIBILITY In chapter 5 is clearly shown that it is possible to make an attractive redesign for a specific WBS 70 building block. It’s possible to change the unattractive forthcoming of the buildings as well as to change the shortcomings in the original design. Making larger housing units isn’t an architectonical and technical problem either. The main problem concerns the financial aspects of the renovation. An educated guess estimates the redesign on about € 40,000,000. It depends on both the book value and the location of the building whether this investment is feasible. The book value of most of the WBS 70 buildings is to high to allow this kind of investment; therefore it’s necessary to obtain large subsidies of local, federal or European governments and institutions. About “location” could be said that nowadays a good location for renovating WBS 70 buildings are the buildings with a free view at the outer edges of the urban area. This results in a migration of people from the high-density urban centers to the low-density outskirts and leaves the centers completely desolated, waiting for more people to leave. Therefore it’s necessary to make an urban redesign for areas like Marzahn in such a way that the centers instead of the boundaries become the most interesting locations to live because of their urban atmosphere and facilities. A very useful way of generating money for a high standard renovation of WBS 70 housing blocks is selling the renovated units. It’s easy to mix owner-occupied properties and rented flats in one building block because of the separated staircases, serving around 25-35 housing units. One part of the building can be sold without having the problems rented flats spread over the whole building block. 7 DISCUSSION The research has shown that it is technically possible to convert an unwanted WBS-70 residential building block into a modern , attractive apartment complex that could be loved by different types of people. There are two problems in the process of converting deserted plattenbausiedlungen into most wanted urban areas. The first problem concerns the neighborhood. It is of no use to convert one WBS-70 complex (approx. 600 housing units) into a modern apartment complex when all the other complexes, commercial services and public spaces stay like they are. An integrated ap-
50
A Future for WBS 70 – The Franz Stenzer Building Block as a Case Study
proach is necessary. This approach is not easy to establish but is conditional to bet rid of the dull and unpopular image of the neighborhood. The second problem concerns money, necessary for the huge investments. An integrated approach means that many private and governmental institutions must cooperate in restructuring the WBS-70 neighborhoods. This also means that a lot of effort (and money) is needed from local governments. In the case of Berlin this will be impossible to realize because the city is almost flat broke. 8 REFERENCES Aanbeveling 25 – korte ankers in beton – berekening en uitvoering; Civieltechnisch Centrum Uitvoering Research en Regelgeving; 20022 Achenbach, H. et al; WBS-70-Grundregeld für Bauelemente – Beton-Stahlbeton-Spannbeton; Heft 30 der Bauforschung; Bauacademie der DDR – Institut für Wohnungs- und Gesellschaftsbau; Berlin; 1975 Berliner Mietspiegel Braat-Eggen, P.E., Luxemburg, L.C.J. van; Geluidwering in de woningbouw; SMD BV, Leiden, 1993; ISBN 9021280340 Brouwer, J. e.d.; De Inbouw – Technische aspecten van flexibiliteit; OBOM, Delft, 1999 Buuren, Jos van; Afstudeerrapport Haak, A.H.G. in den, Quist, P.G., Saenen, E.P.A. (red); Seriematige woningbouw – Bouwen MBO semester 4; ThiemeMeulenhof, Utrecht/Zutphen, 2001; ISBN 900690015X Hordijk, D.A.; Possibilities and problems for post-installed anchors used for changing concrete structures; In: Urban Heritage and Building Maintenance – Concrete; Publications office faculty of architecture; Delft; 1999; p. 95-104 Koncz, T; Handbuch der Fertigteilbauweise mit großformatigen Stahl- und Spannbetonelemente – Konstruktion, Berechnung und Bauausführung – BAND III; Bauverlag GMBH; Wiesbaden-Berlin; 1974; p. 232-233, p 321-328 Koop je eigen Bijlmer. Zeggenschap als instrument voor woonkwaliteit een idee van bewoners, uitgewerkt door IGG/CASA in opdracht van de Werkgroep Verkoop voor Verbetering Luxemburg, L.C.J. van, Raijmakers, T.M.J.; Geluidverbetering bij woningverbetering; SMD BV, Leiden, 1997; ISBN 9021290952 Ott, Thomas; Ein interaktives Model zum Flachennutzunswandel im Transformationsprocess am Beispiel der Stadt Erfurt Quist, W.J.; Leerplan: Een herontwerp voor 11-laagse, prefab-betonnen portiekflats in Marzahn (Berlijn, D), 2002 Quist, W.J.; Afstudeerrapport: Een toekomst voor WBS-70 – Een herontwerp voor 11-laagse prefabbetonnen portiekflats in Marzahn (Ooost-Berlijn); 2003 Stigt, Joop van, e.a.; Renovatie en Onderhoudstechnieken; Technische Universiteit Delft, Delft, mei 1995 VBI Actueel, nr 2, mei 2002 VBI Actueel, nr 6, maart 2003 Verhoef, L.G.W.; Changes in concrete structures for future use; In: Urban Heritage and Building Maintenance – Concrete; Publications office faculty of architecture; Delft; 1999; p. 29-41 Vogdt, F.U.; Preservation and Modernization of Industrially Constructed Residential Buildings especially in former East Germany; To be published in proceedings of the international workshop on the occasion of COST C16, Delft; 2003 http://www.wowi.de/info/sonstiges/bauarten.htm http://www.wbg-marzahn.de/stadtumbau/index.htm http://www.iemb.de/veroeffentlichungen/infobl%E4tter/inf94_05.htm http://www.aisslinger.de http://www.cbs.nl http://www.stadtentwicklung.berlin.de
Creating Flexibility for Better Use of Space in Dwellings in Multi-storey Buildings L.G.W. Verhoef Faculty of Architecture, Delft University of Technology, The Netherlands
N. Hendriks, H. van Nunen & R. Laurs Faculty of Architecture, Eindhoven University of Technology, The Netherlands
ABSTRACT: The paper focuses on some possibilities for enlarging openings in the existing bearing walls in concrete or brick buildings. In the examples shown, enlarging of openings did not always lead to flexibility. Possibly the opening may have still been too small to reach a flexible solution for future tenants or owners. In the case of the example of a pilot project, an entire bearing wall was removed and replaced by a rigid steel frame. The question that arises is in such a case is whether too much support has been taken away. An alternative to this pilot project is described.
1 INTRODUCTION The stock of multi-storey residential units in the Netherlands built during the period 1950-1980 had a programme of requirements which was related to the severe shortage of dwellings in the Netherlands. This shortage was increased because, although the size of families was decreasing, the number of households needed continued to increase. Even today, about 60 years since the end of the Second World War, there is still a shortage of housing. During the post-war decades it became clear that that new building methods would be necessary if more dwellings were to be completed in a shorter time. In the period up to 2000, 46% of the houses had been built between 1945and 1979. Even today the number of houses still fails to meet the needs and the quality of the houses certainly fails to reach the contemporary or future quality requirements. The quality requirements relate to several aspects including the location, with regard to social safety, and architectural and technical aspects. One of the architectural aspects is the flexibility of function within the dwelling itself. The dimensions of rooms, and consequently the floor spans, were often small. To reach a more flexible situation requires that solutions have to be found by creating wider openings in bearing walls than the door openings that merely provide access from one room to another. In principal three ways can be followed: - Openings can be enlarged enough to reach ‘flexibility’; - Openings can be enlarged, but the addition of columns still ensures adequate support; - The entire bearing wall can be removed and replaced by a rigid frame. 2 ENLARGING OPENINGS 2.1 Openings sufficiently enlarged to reach flexibility In the blocks of flats chosen as a demonstration model, the foundations are on piles over which foundation beams connected to an in situ concrete floor are laid. The skeleton consists of cast in situ concrete floors and walls. In this case the walls still had rebars. In later systems the walls Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
52
Creating Flexibility for Better Use of Space in Dwellings in Multi Storey Buildings
were made without rebars, with the exception of 2 vertical rebars at the end of the walls and also 2 rebars above and under the walls. The rooms on the ground floor are the same height as those of the upper storeys, which makes it easier to change functions, for instance, to replace storage space on the ground floor by dwellings. The floors above the ground floor were constructed at the same time as the walls by using narrow tunnel shuttering. The widest floor spans are only 4 metres. The thickness of the floors is 120 mm, while the vertical slabs are 180 mm thick. The cantilever beams for galleries and balconies are made of prefabricated concrete, mounted in or on the tunnel formwork and attached to the bearing construction by reinforcements. The concrete walls provide the stability of the building in both transverse and longitudinal directions.
Fig.1 Existing situation of the multi storey ‘Hoogoord’ block
The openings in the bearing walls are small (see Fig.1). There is twofold advantage to the widening of the openings. Firstly, a much wider view can be obtained. Secondly there is the freedom that can be reached for tenants or owners to use the space according their individual wishes.
Fig.2a Original plan with limited view to the outside world
Fig.2b Proposal for extended view
If every second floor is opened little change occurs to the structure as a whole. In principal, the mechanical system stays more or less the same because the stiffness of the wall in the area of the openings does not change. Moreover, the shear forces on the end column do not increase. Bending moments in the concrete walls do increase, but in relation of the height of the wall, pressure and tension forces should remain small and the stress will not exceed the ultimate value.
Creating Flexibility for Better Use of Space in Dwellings in Multi Storey Buildings
53
Fig.3 Possible interventions
If it is desired that wider openings are created on every floor the situation changes, especially for the end column. It is necessary to make calculations, especially for the columns in lower positions. This solution also has effects on the beams above the openings. The height from floor to ceiling is 2.8 m that means that 0.7 m of concrete wall remains above the door openings. This concrete thus works as a beam. The shear stress for concrete that is not reinforced is the boundary condition for wide openings in the walls. Assuming an available height of only 0.6 m, a wall thickness of 0.18 m and a calculation value for the vertical shear stress of 0.65 N/mm², a shear force of about 70kN can be absorbed. With the existing floor span of 3.6 m, a floor thickness of 0.12 m, with a finishing layer of sand-cement of 0.05 m and an imposed service load of 1.5kN/m² gives a calculated value of 25.7 kN/m and allows a free opening of more than 5 metres. These dimensions are not usually required. Even so, assuming a span of 5m, the maximum support moment is about 60kNm. Depending on the type of steel chosen, between 280 and 450 mm² of steel must be added on the upper side of the beam and half of this value on the under side of the beam. Protection against fire can be provided by a covering of shotcrete. Now solutions are available making use of CFRP instead of steel.
Fig.4a Example of restrengthening of a floor by CFRP in Wien, Austria
Fig.4b Restrengthening of brickwork with CFRP – laboratory test in Delft
54
Creating Flexibility for Better Use of Space in Dwellings in Multi Storey Buildings
The presence of a beam of 0.6 metres under the floor provides a technically sound solution. Nevertheless such a beam imposes a visual separation. For good use of space, solutions that permit the removal of the wall in the position of the desired opening must be sought. A free span for a 0.12 m thick floor could be up to 3.6 metres. The biggest problem is that in the floor there is scarcely any reinforcement running in the direction of the walls. This problem must be solved. By removing the sand-cement layer of 50 mm from the top of the floor and replacing it by a 50 mm thick layer of concrete. In this case rebars, for the stress forces at the supported sides of the floor, can be easily placed before the in situ concrete layer is poured on top of the existing 120 mm floor. For sound proofing 170 mm of concrete still does not fulfil the contemporary demands, so a layer of compressed rockwool will be placed on top of the concrete floor and covered by 50mm anhydrite. Eventually, a floor heating system can be incorporated. Alternatively, the rockwool can be placed on the false ceiling under the floor. The latter solution has the advantage that the connections between gallery and the inside of the dwelling remain the same. More over 50 mm of the original beam can stay and that makes sawing into the wall easier. To accommodate the stress forces on the underside of the floor some strips of carbon fibre reinforced plastic can be glued to it. After the strengthening with steel rebars on the top and with CFRP on the underside of the floor, it is necessary to remove concrete from the opening by drilling and sawing. Some centimetres of the original beam will remain under the floor. The desired appearance can be obtained by designing a false ceiling about 60 mm under the concrete floor structure.
Fig.5 Example of the renovation of a post-war dwelling: The problems of re-dividing the dwellings are visible
Creating Flexibility for Better Use of Space in Dwellings in Multi Storey Buildings
55
2.2 Openings are further enlarged, but the addition of columns still ensures adequate support; The system is very simple. Columns must be added in the desired positions; part of the slab must be sawn out (for concrete) or broken out (for brick), creating suitable conditions for the installation of the new prefabricated or in situ manufactured columns. It is not necessary for the columns to contribute to the stability because sufficient other elements remain to provide this. The biggest problem related to flexibility is that the freedom to make changes remains limited, which is why the proposed solution does not entirely fulfil the real need to change. The problem is illustrated by the following example shown to make the problem clear.
Fig.6a Multi storey tenement house
Fig.6b Original floor plan
Fig.7 Step 1, 2, 3 - Removing façade - Positioning supports to bear the floors - Horizontal -form supports for stability
Fig.8 Step 4, 5 Sawing away a part of the floor Drilling cores out of the bearing wall and sawing of the wall
56
Creating Flexibility for Better Use of Space in Dwellings in Multi Storey Buildings
Fig.9 Step 6, 7 - Removing the last part of the bearing wall - Visible the ‘dry core’ prefab floor
Fig.10 Step 8 - Positioning rigid steel frame
Fig.11 Step 9, 10, 11 - Connecting formwork against the underside of the rigid steel frame - Positioning rebars - Completion of the structure with in situ concrete
Because only one of the four bearing walls was demolished for the test, it was not possible to apply all the principles of IFD technology to every detail. The consequence of the removal of such a bearing concrete wall is that also parts of the floor slabs have to be demolished. After the installation of the new steel supported frame, the missing part of the floor has to be connected to the steel frame by installing in situ concrete with rebars.
3
CONCLUSIONS
It became clear from the test that to create the most desirable degree of flexibility it is necessary to do quite a lot of demolition work. This is clearly shown by the photographs. Not only must
Creating Flexibility for Better Use of Space in Dwellings in Multi Storey Buildings
57
the bearing concrete wall and a part of the concrete floor be removed, but also the facade. An extra problem arises in relation to the stability of the building during the execution of the intervention, which made it necessary to connect parts of the building by means of U-form steel structures. It might be much easier to remove only part of the bearing wall and to replace that part by a rigid frame. Sixty centimeters of the concrete wall is connected to the stays of the facade. In that way a smaller rigid bearing frame could be erected and connected to the sixty-centimeter concrete walls. The facade could remain unaltered. Of course additional materials are necessary to raise the quality of facade and openings such as windows in the facade. The advantages then are that there would be less waste and lower costs. This may make possible the use of using more realistic options for renovation, rather than choosing demolition.
L_living room K_kitchen S_bedroom B_bathroom
Fig 12a: Alternative floor plan that shows that removing the total wall is not necessary. L_livingroom1 K_Kitchen S_bedroom
B_bathroom
Fig 12a: Alternative floor plan that shows that removing the total wall is not necessary.
58
Creating Flexibility for Better Use of Space in Dwellings in Multi Storey Buildings
REFERENCES Verhoef L.G.W. 1999. Changes in concrete structures for future use. International congress on urban heritage and building maintenance-Concrete. Publication Office Faculty of Architecture, pp 111-121 ISBN 90-5269-274-2 Hendriks N.A., Nunen H. van, Rutten P.G.S. 2006 IFD Technology for the Renovation of Apartment Buildings: Project Flexible Breakthrough. Internal publication Technical University Eindhoven. Schaur C. 2004 Strengthening of a concrete slab with FRP strips Improvement of Building’s Structural Quality by New Technologies, Outcome of the Cooperative Activities. A.A. Balkema Publishers, Leiden, The Netherlands, a member of Taylor&Francis Group plc, pp 559-563 ISBN 0415366100 Van Zijl G.P.A.G. and Verhoef L.G.W. 2002. Restrengthening of brickwork to reduce crack width with C.F.R.P. Advances in Engineering Software 33(1), Elsevier Science, 49-57 Van Zijl G.P.A.G., De Vries P.A., Verhoef L.G.W. and Groot C.J.W.P. 2003. Experimental confirmation of predicted restrained shrinkage damage in masonry walls. ICPCM-A new era of building, Cairo, Egypt, Feb.18-20
Restoration of the ‘Planeten flats’ in Helmond L.G.W Verhoef Faculty of Architecture, Delft University of Technology, Delft, The Netherlands
F. Maas Arch. en ing.-buro KOVOS, Eindhoven, The Netherlands
J. van der Boomen Adviesburo F. Tielemans bv., Eindhoven, The Netherlands
ABSTRACT: The interventions in the ‘Planeten Flats’, which from both architectural and technical points of view was a monotonously repetitive, building, were so spectacular that in 1993 the renovation project was awarded the ‘National Renovation Prize’. In particular the architectural changes which resulted in a clear position of the entrance, the changes in the facade that divide the building into three distinct horizontal layers, and the spacious winter garden with a multi purpose function, give the building a pleasing integrated modern look. In themselves the techniques necessary to reach the architectural goals were not spectacular, but the many technical difficulties that had to be faced are worthy of description. These include different temperature movements in elements that are partially standing and partially suspended and the complicated method used to remove bearing walls and replace them by prefabricated concrete columns to bear the steel beams as supports for the bearing walls above.
1 GENERAL DESCRIPTION OF THE AREA In the Netherlands residential blocks of flats have been built is a variety of forms, using many types of system and varying in length and height. In the city of Helmond the plan for ‘de Eeuwsels’ residential area called for the construction of 7 multi storey residential blocks. The plan included some thousands of dwellings, a shopping area, schools and housing for elderly people. The 7 multi storey residential blocks are positioned next to a tree lined route that connects the shopping area on one side to the northern border of the city that is formed by the river ‘de Aa’. By the nineties, when new areas were being designed and new buildings were replacing existing buildings, the accent shifted from the need for quantity to raising the standard buildings to improve the quality of life of the residents: architecture became more important, the surroundings became an integrated part of the residential quality. Because the existing Planeten Flats no longer fulfilled the contemporary demands, people chose to look for better living conditions and moved out. In 1991 four architect’s practices were invited to submit proposals for renovation and the ‘Kovos’ practice, with architect Paul Vlemmings, was awarded the commission to renovate 2 of the 7 multi-storey residential blocks. Two blocks were demolished, while 3 other blocks were renovated by the architects of the ‘Topos’ practice The problems relating to quality of the ‘Planeten Flats’ derived from its appearance as an anonymous concrete structure without specific architectural features. It was merely the result of a practical building system without any distinguishing features. Each dwelling was exactly the same as that of the neighbour. The entrance was simply the space that was left within the concrete structure to accommodate the elevator and stairwell. Such blocks of gallery flats built according to the ‘Neduco’ system have no architectural accents.
Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
60
Restoration of the ‘Planeten flats’ in Helmond
Fig. 1 a. Existing plan of a dwelling; b. New plan; c. Alternative plan of bathroom with shower instead of bath
Fig. 2: Original situation
Fig. 3: After renovation
The design of the architects who were commissioned to renovate the building, was intended to enlarge the spaces in the individual dwellings by connecting two bedrooms to make one, enlarge the shower cell to provide a complete bathroom and increase both safety and comfort. A
Restoration of the ‘Planeten flats’ in Helmond
61
considerable part of the budget was used for installations, improvement of the kitchen, improvement of the insulation and window frames, painting etc. The most important part of the design was threefold and had structural implications: - to create a more spacious entrance hall, including a winter garden; - to enlarge the balconies - to design dwelling floors for elderly residents. They will have a closed access gallery. The new facade was constructed from insulated heavy concrete elements, partly standing on flat columns, partly suspended from a structure on top of the roof. 2 STRUCTURAL PROBLEM The structure itself was safe and sound. The concrete structure presented no problems, the main changes involved adaptations of the structure to incorporate the desired new architectural qualities, including: - the creation of a new space around the entrance including, a winter garden; - the enlargement of the balconies and - the provision of closed access gallery on the floors designed for elderly residents. 2.1 Typology of structures The block of flats is a composite concrete structure. Walls and floors were constructed from poured in situ concrete. The cantilevered beams were prefabricated and placed on the system formwork. Anchors projected from the cantilevered beams and penetrated the formwork. The beams were connected to the walls after the concrete has been poured into the formwork of the wall, and had hardened. This type of structure became known as the NEDUCO system. In this particular system the first floor was laid slightly lower than the ground level, while the surrounding beams were situated about 0.7 m deeper than the ground level to ensure that the beams were not affected by frost during winter . 2.2. Problems To create the new entrance hall, including a winter garden, it was necessary to remove a bearing wall with connecting floors over three storeys. The vertical load had to be transferred to the foundation beams by four new columns extending from the underside of the concrete floor slabs of the fourth storey. New larger balconies were also connected to the structure. The extra load had to be supported by the walls. 2.3 Actions All the actions were focused on the system of bearing walls and floors. The walls were the stiff elements of the structure. Where the building had to be extended to accommodate a new stairwell a shallow foundation had to be constructed for this. To create space for the winter garden, bearing walls were removed over the lower three floors, while the upper floors had to remain undisturbed. 3 DESCRIPTION OF WORKS 3.1 To create a new space for an entrance and a winter garden. To create the spacious winter garden, the second and the third level floors had to be removed on both sides of the central bearing wall in this area. It was also necessary to removed this bearing wall up to the fourth floor level, while the bearing wall above that level had to be supported
62
Restoration of the ‘Planeten flats’ in Helmond
by four prefabricated concrete columns ø 400 mm and a steel beam HE340B on top of the four columns and under the in situ concrete wall that extended from the fourth floor to the roof.
Fig. 4a: Realisation opening for winter garden
Fig. 4b: Rear view of the residential block with balconies above the winter garden
Fig. 5: During execution
Fig. 6: Inside view
Fig. 7: Inside view
Restoration of the ‘Planeten flats’ in Helmond
63
Normally it is relatively easy to replace a concrete wall by columns. With a diamond covered saw part of the concrete wall is sawn out and new prefabricated columns are placed in the openings that have been created. The gap above the prefabricated columns and under the in situ concrete wall is then filled with shrinking free mortar, see Fig. 8. After that the part of the concrete wall that remains beside the prefabricated columns can be removed. The fact that floors connecting the bearing wall above the new prefabricated columns to bearing walls running to the foundation ensures that there will be no stability problem.
Step 1: Sawing out a part of the vertical
Step 2: Pacing new columns in the ope-
slab
ing after removing the wall.
Fig. 8 To replace a concrete wall by columns
The difficulty with the ‘Planeten Flats’ was that the bearing wall is not a continue slab but a slab with large openings, see Fig. 9. This is why the architect chose to place a steel profile (HE340B) under the concrete wall and above the prefabricated concrete columns. Because of the length of the concrete columns is about 7.5 metres they were divided into 3 elements of 2.5 metres and welded to each other in situ. The steel profileHe340B also consisted of 3 elements. One end element had to be placed on top of two concrete columns. This part of the steel beam has a cantilevered end part, necessary to support part of the closed facade elements, later on. Execution steps: a. sawing openings in the floor in the positions of the new columns; b. sawing openings in the floor for the temporary support structure c. sawing openings in the bearing wall for the new columns d. drilling openings in the wall just under the fourth floor and above the third floor for insertion of ͝ profiles made of HE120B. e. Positioning of the temporally support system on both side of the concrete wall with on top a HE300B profile for supporting the short HE100B profiles; f. Inserting HE100B profiles through the wall and resting them on the HE300B. Filling the gap above the HE100B and under the concrete wall with shrinkage free mortar. g. After hardening of the concrete, the temporary support system is brought under pressure h. The horizontal part of the bearing wall where the profile HE340B has to be placed is removed. The weight of the bearing wall from the fourth floor up is now transported to the g round floor by means of the HE120B and the temporary support system. i. Placing of the prefabricated concrete column elements and connecting them together to form one continuous column. j. Placing the steel profile elements in position by means of anchor bolts on the prefab columns and filling the gap between concrete column and steel HE340B profile and the gap between HE340B profile and the in situ concrete bearing wall above with shrinkage free mortar. Some days for hardening. k. Relaxing the temporary structure and removal of the HE100B profiles. l. Removing the remaining part of the concrete walls and floors that are no longer required.
64
Restoration of the ‘Planeten flats’ in Helmond
Fig. 9 Section of the original structure
Fig. 10a Temporarily support structure
Fig. 10b Mounting final structure of concrete columns with HE340B on top
Restoration of the ‘Planeten flats’ in Helmond
65
Fig. 11 End situation of the assembling of the bearing structure of the winter garden
Fig. 12 Steel structure of the fourth floor of the winter garden
Fig. 13 Steel beam HE 340B in three parts
REMARK: Altogether quite a complicated system is required to bear the floors from the fourth floor up to the roof. As stated earlier, it is relatively easy to replace a concrete wall by columns. In this case one option could be to connect the free standing bearing wall elements on the fourth and fifth floors. This could be done for the missing wall parts above 2.1 metres. The walls are connected after adding chemical anchors and removing the floor elements above the formwork and filling the formwork with in situ concrete. The wall is now continuous, with holes to a height of 2.1 metres and a maximum width of 1.25 metres. The distance from floor to floor is
66
Restoration of the ‘Planeten flats’ in Helmond
2.8 metres, which means that the concrete above door openings could be 0.7 metres, so more than enough to reach this target. As an alternative instead of steel rebars a solution could be found by using carbon fibre reinforced plastics 3.2 The closed access gallery.
In the redesigning of this residential block the 4th and 5th floors were intended for occupation by older residents. In the description of works it became necessary that the gallery should be closed so that the residents would not have to walk along the gallery in inclement weather. New concrete facade elements were added. The bearing system for the concrete facade elements was rather complex. This was necessary to improve the architectural image of the renovated residential block, and produce an architectural system of three horizontal areas and three vertical areas. That is why at the end of the gallery, the concrete facade elements are supported by vertical concrete slabs. The slabs are supported by a new extension of the foundation supported by concrete piles. The middle parts of the concrete facade elements are executed as a system that carries the load up to the roof by tensile tubes 80.80.4 mm. On the roof itself are trusses to connect these forces to the bearing concrete walls. The last part of the concrete facade is supported by cantilevered steel beams over new columns above the winter garden. This forms a complex system of suspended elements with different temperature movements.
Fig. 14 Architectural expression of the form of the façade.
a. b. c. d.
New concrete supports for new concrete façade elements New concrete façade elements carried by tensile tubes to the roof structure Stairhouse with elevator Closed end wall
Restoration of the ‘Planeten flats’ in Helmond
67
Fig. 15 Truss standing on the roof
Fig. 16 Connecting prefab façade elements to cantilevered beam
3.3 The enlarging of the balconies. For the enlarging of the balconies the vertical concrete bearing slabs are used as the most important system. The extensions of the balconies have been constructed as concrete slabs surrounded by UNP 200 for the outer sides and L 150.75.12 as connections to the existing ends of the concrete balconies. On one side the UNP is connected to the bearing construction by chemical anchors and on the other side is connected to a framework made from tubes 120.60.4 mm which are also connected to the bearing walls by chemical anchors.
Fig. 17 Rear view of the planetenflat with balconies
Fig. 18 Top view on the balcony
68
Restoration of the ‘Planeten flats’ in Helmond
Fig. 19 Section AA
Fig. 20 View separation that acts as a framework to transport the load of the balcony to the bearing walls
4 CONCLUSION The renovation of this residential block has resulted in the upgrading of the dwellings to an acceptable level and improved the quality of life of the residents, while the changes in the architectural system have improved the appearance of the building and the residential area in which it is located. In the system that has been described the bearing structure gave rise to quite serious problems. This illustrates that it is worthwhile investigate whether special problems can be solved by using new techniques or a different philosophy in relation to solving problems such as that described under ‘Remark’. REFERENCES [1] Debets C. Helmondse flats ondergingen metamorphose Bouwwereld nr.1 (3 februari 1995) [2] Vlemmings P, 1995. Flats krijgen nieuw hart. Architectuur &Bouwen 3-1995 pp18-21 [3] Verhoef L.G.W. 1999. Changes in concrete structures for future use. International congress on urban heritage and building maintenance-Concrete. Publication Office Faculty of Architecture, pp111121 ISBN 90-5269-274-2
Rebuilding Modern Housing for Increased Sustainability Sonja Vidén School of Architecture, Royal Institute of Technology, Stockholm, Sweden
ABSTRACT: This paper presents a number of structural building measures in the residential area Markbacken in Örebro, Sweden. The refurbishment programme was directed towards solving technical problems due to ageing materials and new demands for sustainability, especially for energy saving, and towards making the declining area more attractive on the housing market. The main challenges here, like in most of the post-war housing stock of Sweden, was to improve the accessibility for handicapped, to repair and enlarge balconies, and to add new ones, to adapt flat sizes to the local demands, and to improve the entrances to the buildings, at the same time preserving and carefully developing the architecture. 1 GENERAL DESCRIPTION OF THE CASE STUDY In the late 1990s, extensive governmental subsidies for Local Investment Programmes (LIP) were raised in Sweden to stimulate a faster development towards a sustainable society. Means were granted to environmentally friendly measures of all kinds, from regional heating systems to local waste-water treatment and new energy saving components in buildings. Especially in housing refurbishment projects, not just technical measures but also social and cultural matters were taken into consideration in the programmes granted. In Sweden, prefabricated panel buildings represent less than 20 percent of the multifamily housing stock of the so-called “record years” (1961-1975), and fairly few problems concerning structure are caused by the building methods used. One common problem is carbonisation and moist injuries to concrete constructions, such as balconies, prefabricated panels with exposed aggregate, and parking decks. Equally common are the “secondary” problems which arise when adjustments to new and local needs demand more or less extensive interventions in the structure. Many rebuilding programmes include installation of lifts, enlarging balconies, merging flats to bigger ones or subdividing them to smaller to meet new needs, and improving the connections between yards and traffic/parking side of the buildings. The residential area Markbacken is an example of the “secondary” problems mentioned above. The area was built 1958-1963 in Örebro, a city of about 125 000 inhabitants in mid-Sweden. The developer was the municipal housing company Örebrobostäder AB (ÖBO), still the owner of the area. In all, 1 194 flats, with a surplus of 2-bedroom flats, were built in 3-4-storey slab blocks. U-formed blocks were partly connected to each other by 1-storey service buildings, thus creating spacious inner yards intended to be free from car traffic (Fig. 1).
Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
70
Rebuilding Modern Housing for Increased Sustainability
Figure 1. The district Markbacken, Örebro
Local facilities like a small local centre, school and day-care units, and a central park, were planned and built in the area. Over the years, the primarily good status of the area on the local housing market turned into segregation and social instability. The building envelopes caused increasing maintenance problems and energy losses. About 1996, a moderate renovation of three buildings in the east part of the area started. In 1998, an application for LIP subsidies was granted. The rebuilding did not start until April 2000, though. The decision process took a long time, partly because of the great stress laid on the tenants´ influence on the rebuilding programme. The residents and the professional parties were deeply engaged and several meetings were held. Since the LIP project had to be completed in 2002, due to the grant regulations, this part of the rebuilding was reduced to just one stage, comprising 158 flats (rebuilt to 148). Slab blocks of similar size, partly used for offices and the like, were rebuilt at the same time, without special grants. Two more rebuilding stages were completed 2005. Some measures were changed from stage to stage, for technical and economic reasons, and to vary the design. In the final phase, the remaining slab blocks are demolished and replaced by single family rental houses and a tower block specially designed for senior housing. This case study of Markbacken is based on a study of the rebuilding programme and process as a whole, specially focussing the LIP project and the relations between environmental goals and interventions, the conditions of the housing area, and the present residents, as well as the environmental effects of the measures. The basic study comprises all kinds of measures taken to reduce environmental shortages and improve the technical and social status of the area. Many of the interventions concern both structural components and envelope, and are so closely connected to each other that it seems natural to describe them all together. Nevertheless this paper is concentrated to problems concerning structures.
Rebuilding Modern Housing for Increased Sustainability
71
2 PROBLEMS CONCERNING STRUCTURES 2.1 Typology of structures The general structure of the buildings is the very common “book-shelf”-like framework of site cast concrete floor structure and transverse inner walls and gable walls. Due to the U-forms and plans for commercial spaces in the bottom floors the constructions are partly more complicated, though. In some buildings there are also load-bearing core walls, and in several parts of the bottom floors concrete pillars are taking loads from the construction above, just like the slim concrete pillars which are structural components connected to the external panel walls. Gas concrete panels were used for light (not bearing) inner walls. The external walls of the bottom floors were all plastered gas concrete masonry. The external walls of the upper floors were constructed in various ways, with various materials: gas concrete masonry outside all staircases and bathrooms, otherwise prefabricated gas concrete panels with a mineral wool core, or wooden curtain walls with mineral wool covered by windbreaking asbestos panels. The different kinds of external wall constructions of the upper floors were all covered by asbestos cement facade panels on wooden joists. (Fig 2).
Figure 2. Gable facade in its original shape (left). The construction revealed during demolition in stage 4 (right)
The roofs are slightly sloping (ca 10o). They were given a very unusual construction, which reduces the distance between the eaves and the ground and still admits a room height according to actual building codes. A mansard roof structure of concrete was covered by a slim wooden construction with 10 cm mineral wool insulation, and covered with roofing felt. In the inner corners of the yards, porticos through the bottom floors connected the yards with the parking areas outside the “meander” loop of buildings. Although the staircases, with small windows, were facing the outside of the “meander”, their only entrances faced the yards. There were no lifts in the original buildings. Up to 1977, due to the building regulations, even many 4-storey houses could be built without lifts. The flats were of various sizes, with a surplus of 2-bedroom-flats. In the bottom floors many small, single-room flats for 1- or 2-person households were built. All flats in the upper storeys got a balcony, some as wide as the room inside it, and inset, with the balustrade in line with the facade (see fig. 2). Some balconies were considerably smaller. The balcony floors were site cast reinforced concrete structures, born by reinforcing bars cast with the indoor floor structures, and in good technical condition.
72
Rebuilding Modern Housing for Increased Sustainability
2.2 Problems Most of the problems notified by the housing company in the first rebuilding programme, or later, in the thorough consultations with the residents and other parties, did not concern the structures of the buildings as such. Still, substantial local changes of the structures would be needed to solve some very urgent problems: - Lack of lifts; poor accessibility for people with disabilities In Sweden today, lifts are demanded in all new buildings with more than two floors. When rebuilding existing housing, this demand can be reduced, according to local conditions and municipal guidelines. For instance, flats in the bottom floors, accessible from ground level, can reduce the demand for new lifts. In Markbacken, several inhabitants were aged people who had been living in the area for a long time but might be forced to move because of the lack of lifts and good accessibility. - Small balconies During the detailed planning process many of the residents expressed strong wishes to have bigger balconies. Several aged residents had problems to get outdoors, and a big balcony would reduce some of the negative effects of their handicaps. In general the balcony slabs were in a good shape technically (which is not always the case). - Inappropriate distribution of flat sizes The surplus of 2-bedroom flats, the shortage of bigger flats, and the single room flats in the bottom floors contributed to the social instability. Growing families wanting bigger flats had to move somewhere else, and many small households found the 2-bedroom flats too expensive. The very small flats in some of the bottom floors had more or less become in-between flats, where several tenants caused disturbing noise and other problems. - Inconvenient passages between yards and parking lots The porticos were narrow, shaggy, and not sufficiently lit; many residents were afraid of using them in the dark hours. The lack of more direct and safe pedestrian passages to the parking lots caused undesirable car traffic in the yards. In addition, the insulation of the floor structure over the porticos was insufficient, and the day-light in the staircases was poor, due to small window openings. 2.3 Strategy for improvements In order to promote a sustainable development of Markbacken the area has to be properly maintained, and adapted to new housing needs and preferences – just like many other large and homogenous housing areas. To achieve such goals several changes of the structures are needed. A special matter is that in Sweden, according to the Planning and Building Law, building renovation shall be carried through with care for the existing qualities and structures, with respect to the architectural character of the building, and – according to the preparatory texts – with care for the residents. This paragraph applies to all buildings, no matter how or when they are built – also to the often depreciated residential areas of the “record years” ca 1960-1975. Thus, the main objective of any structural intervention is to add any wanted quality with as high ambitions and as limited interference and costs as possible.
Rebuilding Modern Housing for Increased Sustainability
73
2.4 Actions The rebuilding comprised several measures, which had to be adjusted to the special conditions in the different buildings and building parts. In addition, the tenants´ influence affected the choice of measures. The main actions concerning structural inventions were: - Installation of lifts in several staircases, quite evenly distributed over the area. According to negotiations between the housing company and the local authorities 30 % of the flats had to be accessible after rebuilding. Three principally different solutions were used, due to different technical and design prerequisites. - Enlarging balconies, giving them different forms to increase the variety of the area, and adding new balconies in special sites. - Merging flats in bottom floor and first floor to maisonettes. - Rebuilding and enlarging passages from the parking side of the buildings to the yards, and adding new entrances to staircases facing the parking side. 2.5 Description of works 2.5.1 New lifts One solution (a) was to use a part of two-bedroom flats alongside the existing entrances. This solution demanded new holes in existing floor structures. The special structure with pillars and load-bearing inner walls diminished the need for special reinforcement. Because of the surplus of 2-bedroom flats, the resulting variation of flat sizes compensated for the loss of housing area for rent. (Fig. 3 and 4).
Figure 3a. Entrance floor before (left) and after (right) the installation of lift.
Figure 3b. Upper floors before (left) and after (right) installation of lift.
74
Rebuilding Modern Housing for Increased Sustainability
Figure 4. The improved entrance with the new lift, more space, and better lighting and materials.
A more frequently used solution (b) was to build new stairs in connection with the existing stairwell, where the flights of stairs were replaced by a lift and a passage. The lift has doors in both ends. (When the entrance is not at the same level as the bottom floor, one flight of stairs has to be kept beside the new lift). The additions to the old buildings, for the new stairways, were designed differently in different stages of the rebuilding, thus adding more variation to the facades. (Fig.5).
Figure 5. Entrance floor and upper floor landings after installation of lift. The section shows the addition of the staircase. Here the new staircase got glass walls, to get much daylight into the landings.
Still another solution, used in a later stage, was to install a lift in an extension of the stairwell, and replacing the original two flight stair with a single-flight stair. (Fig. 6).
Rebuilding Modern Housing for Increased Sustainability
75
Figure 6. Entrance floor after installation of lift in extended staircases. Note the new pillars supporting the extended balconies above the bottom floor.
2.5.2 Enlarging balconies The concrete constructions of the balconies were in quite good shape, technically. This is not always the case; usually carbonisation and/or other damages demand repair especially of the front edge of the balcony slabs. In Markbacken, the balconies were enlarged in different ways. Most of them were just made deeper, by giving them a prefabricated addition born by two long steel bars, fastened to the old balcony slab by screw bolts (Fig. 7). In some locations additions were rectangular, in others curved or triangular. Some small balconies at the corners of buildings were extended around the corner, and given new, rounded forms. A few totally new, rounded balconies were also added. In these cases new, prefabricated concrete structures replaced the old ones. The new balcony slabs, and some considerably extended rectangular slabs, were born by slender concrete pillars, founded outside the existing buildings (see fig. 6 and fig. 11).
Figure 7. The additional balcony slab is born by two steel bars, fastened to the old balcony slab. The light fitting on the side walls of the balconies are fastened on similar steel profiles.
76
Rebuilding Modern Housing for Increased Sustainability
2.5.3 Merging flats into maisonettes In the first and second stage of the rebuilding 19 bigger flats were created by adding certain small flats in the bottom floors to flats above. A hole was cut in the concrete floor structure for an internal, prefabricated wooden stair. All those flats got direct access to a new, private terrace at ground level. The main entrances to the flats were placed there. (Fig. 8, and fig. 9). These flats, with their special design and size, became very popular, and contributed to a much more stable rental situation in the area.
Figure 8 a. Bottom floor before (left) and after (right) merging the flats into maisonettes.
Figure 8b. Second floor after merging the flats into maisonettes. The flat to the left is kept in its original shape and size.
Figure 9 (right). The entrances to the new maisonettes, and to preserved single room flats in the bottom floors, are facing the private gardens which are marked off from the common space of the yards. The design of private gardens and balconies varies between the yards. This maisonette differs slightly from the one shown in figure 8. This garden is not yet planted, but today many flowery private gardens help to make the yards pleasant and vivid.
Rebuilding Modern Housing for Increased Sustainability
77
2.5.4 Enlarging passages between yards and parking lots Some of the narrow and worn down passages were kept, but renovated with new, brighter surface layers and new lighting. Some of the supporting pillars were covered with clinker plates. The insulation of the floor structures above was improved, with some difficulties, since the height of the passages already was reduced by crossing pipes (see photos below). Other passages were also widened and given a softer form. The bearing pillars in the bottom floor made this possible without interventions in the main structure (Fig.10). One portico, in the building partly used for offices, was widened and made two storeys high, making use of a part of the second floor. The old floor structure concerned was demolished and the floor structure above the new, enlarged portico was given satisfactory insulation. These extensive interventions demanded special safety shore during the works (Fig. 11a), and new pillars to support the new construction (Fig. 11b, photo).
Figure 10. Layouts before (left) and after (right) rebuilding of one of the widened passages between the parking area and the yard. Photos below: A narrow passage seen from the parking side, after the rebuilding start (left), and a passage opposite to the one at the drawings, seen from the yard, after completion.
78
Rebuilding Modern Housing for Increased Sustainability
Figure 11a. The section of the passage shows some of the safety shore during construction work.s Figure 11b. The section and the details show the new floor and wall structures above the portico, with the new insulation layers. The photo shows the resulting generous portico facing the block where the local centre is situated.
Rebuilding Modern Housing for Increased Sustainability
79
In parts of the residential buildings, where the stairwells were facing the parking lots, new door openings were made in the external walls at this side of the buildings, from the first landing of the two-flight stairs. If needed, new outdoor stairs were constructed to admit the entrance to this level. In addition, the windows of the stairwell were enlarged, in different ways in different building. The new, big windows got energy saving thermopanes. The interventions in the external walls did not demand any special reinforcing measures. A very positive effect of the new, direct connections to the parking side of the buildings, is that the unwanted car traffic in the yards practically seized. (Fig 12; see also Fig. 3).
Figure 12. An additional entrance from inside, and from outside.
3 CONCLUSIONS The refurbishment of Markbacken is representative of many types of problems and interventions in housing areas built during the ”record years” in Sweden. Here, as in other cases, the overall ambition to make the area more varied and attractive at the housing market has been an important driving force when the technical solutions of the problems have been chosen. In many cases, for instance the new lifts, cheaper solutions and designs have been passed over by more attractive and multipurpose ones. The different stages have been designed individually to create variety, which has demanded interventions of many different kinds and varying complexity in the original constructions. Some new solutions have been chosen to avoid disadvantages discovered in the previous stages. The attendant possibility to learn from previous solutions and stages is something to take advantage of in any big project. Other new solutions have been chosen just in order to give the actual building some individual characteristics. This has been encouraged by the housing company by choosing different architects for different stages. Probably the economic advantages of long series of the same solution are less valuable than the long-lasting advantages of a varied environment where individual preferences are allowed to be manifested. 4 REFERENCES Vidén & Botta: Bostadsförnyelse och miljöåtgärder med stöd av Lokala InvesteringsProgram. Hållbar utveckling i 50-60-70-talens bostadsområden. (Housing renovation and environmental measures supported by Local Investment Programmes. Sustainable development in housing areas of the 1950s, 60s, and -70s) working report 2006 (in Swedish) Botta: Towards sustainable renovation, doctoral thesis 2005 Vidén, Blomberg & Botta: Techniques for sustainability in housing areas from the 1950s,-60s, and 70s, ongoing work, to be completed December 2006.
This page intentionally left blank
Enlargement of Balconies and Upgrading of Existing Residential Building Daskal Kamcev street number 1 in Skopje Zivko Ljube Bozinovski Institut of Earthquake Engineering and Engineering Seismology Skopje, F.Y. Republic of Macedonia
Kiril Gramatikov Civil Engineering Faculty, Skopje, F.Y. Republic of Macedonia
ABSTRACT: For the needs of the occupants, only a light weight attic within the frames of the existing structural outline has been designed. Considering that the construction of the attic will also involve terraces, these must not rest on the additionally constructed terraces but on their own cantilever structure resting on the newly designed beams in the transverse direction. The additionally constructed terraces cannot sustain any additional load from the attic. 1 GENERAL DESCRIPTION OF THE CASE STUDY The existing structure consists of a basement, a ground floor and two storeys. The bearing structure of the building consists of bearing walls constructed of solid brick in both orthogonal directions, with horizontal but no vertical RC belt courses (Fig. 1-8). The floor structures consist of reinforced concrete finely ribbed floors with a total thickness of d=35.0 [cm]. The structure is founded on RC strip foundation. The roof structure also represents a RC floor surmounted by a timber roof structure. For the needs of the occupants, only a light weight attic within the frames of the existing structural outline has been designed. Considering that the construction of the attic will also involve terraces, these must not rest on the additionally constructed terraces but on their own cantilever structure resting on the newly designed beams in the transverse direction. The additionally constructed terraces cannot sustain any additional load from the attic. The weight of the structure in its new conditions will be Wvk-nova =20535 [kN]. The weight of the existing structure is Wvk-pos =18140 [kN]. The additional load added to the existing structure by the construction of the attic accounts for 13.20% of the total mass of the existing structure.
Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
82
Enlargement of Balconies and Upgrading of Existing Residential Building in Skopje
+3,00
+3,00
+3,00
+3,00
Figure 1. Plan of The First Storey, Residential building, Daskal Kamce 1 Skopje, Existing
+9,00
+9,00
Figure 2. Plan of New Upgraded Storey, Residential building, Daskal Kamce 1 Skopje, New
nadgr adba
Enlargement of Balconies and Upgrading of Existing Residential Building in Skopje
+ 1 1 .5 0
+ 9 .0 0
par ket sl ep pod M K "A V R A M E N K O " l et vi t r sk a + 6 .0 0 ma l t e r
+ 7 .5 0
+ 4 .5 0
+ 3 .0 0
+ 1 .5 0
± 0 .0 0
-1 .3 5
-2 .6 0
Figure 3. Cross section, Residential building, Daskal Kamce 1 Skopje, New
Figure 4. Fasade, Residential building, Daskal Kamce 1 Skopje, New
83
84
Enlargement of Balconies and Upgrading of Existing Residential Building in Skopje
Figure 5. Fasads, Residential building, Daskal Kamce 1 Skopje, New
Figure 6. Enlargement of Balconies transformed into residential areas
Enlargement of Balconies and Upgrading of Existing Residential Building in Skopje
Figure 7. Enlargement of Balconies transformed into residential areas
Figure 8. Enlargement of Balconies transformed into residential areas
85
86
Enlargement of Balconies and Upgrading of Existing Residential Building in Skopje
2 PROBLEM CONCERNING STRUCTURE 2. 1. Typology of structures The bearing structural system consists of bearing walls constructed of solid brick in lime or cement lime mortar, in both orthogonal directions, strengthened and inter-connected by horizontal RC belt courses at the level of the floor and roof structures. The disposition of the walls depends on the distribution of the premises, the direction in which the floor structure is supported, the outlets beyond the outline of the structure, the horizontal and the vertical communications. The structure is founded on concrete strip foundation. The floor structures are precast RC fine ribbed type AVRAMENKO. The roof structures are constructed of timber, with roof cover most frequently constructed of ceramic tiles. 2.2. Problems a) Damages Due to the ravages of time, improper maintenance and design/performance defects in the course of time, both types of structures have suffered different extent of damage and require proper maintenance, i.e., increase of seismic resistance to the level compliant with the legislative regulations. b) Interventions The interventions being done on this old residential buildings involve enlargement of balconies that are transformed into built residential areas and building of residential attic. 2.3. Actions a) Loads Vertical – Gravity and Live Loads Horizontal – Wind Load Exceptional Loads Earthquakes b) Actions Age of structures Intervention on structures Adding on the side of buildings (balconies, galleries, rooms) Adding on top Maintenance 2.4. Solutions 2.4.1. Strategy for improvement Repair of damaged structures Revitalization of the existing structures
Enlargement of Balconies and Upgrading of Existing Residential Building in Skopje
87
2.4.2. Description of works The additional attic will be constructed by removal of the excessive load from the roof, construction of a light RC structure anchored into the existing horizontal RC belt courses and placement of a roof cover again.The weight that is added to the existing structure exceed 10% of the total weight of the structure. For the purpose of constructing the attic, the elements and the integral system have been analysed up to the ultimate states of strength, stiffness and deformability of the existing structure. In defining the storey masses, the weight of the planned attic has been added. The characteristics of the material of the existing walls were considered based on knowledge on this type of masonry. The seismic forces have been defined in compliance with the regulations related to masonry structures with RC belt courses. The analysis enabled definition of the strength, stiffness and deformability capacity of each storey and in each direction taken separately. The obtained data give the possibility for comparison with those required with the regulations (Fig. 9-10). Figure 9. Storey P-' diagram, Apartment building DK1, X-X, existing state
Figure 10. Storey P-' diagram, Apartment building DK1, Y-Y, existing state
88
Enlargement of Balconies and Upgrading of Existing Residential Building in Skopje
The results obtained from the analysis (which is particularly clear from the graphical presentations) prove the existence of the possibility of constructing an additional light weight attic on the existing structural system with allowable tensile strength of the existing masonry of 1.0 kg/cm2 and allowable compressive stress of the masonry of 12.0 kg/cm2. It is desirable to use light weight masonry with additional thermal and sound isolation instead of ordinary masonry. Prior to the beginning of the construction and opening of the walls, it is recommendable to check whether the existing masonry really has the characteristics that have been used in the calculations. The considered seismic forces refer to the IX seismic zone, i.e., 16.0 % of the weight of the structure, regarding the existing additional part so that the seismic forces are higher than 17.0 % only at the attic due to the amplification. The forces along the elements have been distributed according to the stiffness of the specific elements. Due to the specific nature of the works, it is necessary to take all the measures for efficient and precise completion of the construction and the handicraft works, whereat particular attention should be paid to anchorage of the reinforcement of the newly designed columns and the reinforcement of the belt courses of the finely ribbed floor. It is also advisable to use all measures for protection during the performance of the works. During the opening of the belt courses where the newly designed columns are to be anchored into the existing structure, it is proposed to use a method for the most efficient anchorage of the reinforcement of the columns with the reinforcement of the belt courses. Welding of the existing and the new reinforcement should be done within a length of at least 20 cm. 3 CONCLUSIONS To satisfy the requirements of seismic design of high-rises in seismically active regions, a modern design concept was aplied, that apart from the strength and deformability take into account the plastic excursions and the capability for seismic energy dissipation. From structural aspects, analysis of the stability of existing structure was made. The results show that capaciti of strength and deformabiliti are great than required by Code. Analysis of the additional load imposed with the construction of the attic Total weight – existing state Total weight – new state Difference between the new and the existing state Additional load/existing state ratio
Wvk-n= Wvk-n= Wvk-n= Wvk-n=
18140 kN 20535 kN 2395 kN 13.20 %
The relative storey displacements in X-X direction amount to Gx-x=0.10 [cm]. The relative storey displacements in Y-Y direction amount to Gy-y=0.11 [cm]. The allowable relative storey displacement for the linear behaviour of the structure amounts to Gmax= h / 350 = 250/350 = 0.714 [cm]. Since a relatively light reinforced concrete structure has been selected, the displacements are considerably lower than those allowed by the regulations.
Enlargement of Balconies and Upgrading of Existing Residential Building in Skopje
89
4 REFERENCES Bozinovski, Lj., Z., “Improving The Quality Of Existing Urban Building Envelopes”, EE-21C, International Conference on Earthquake Engineering, 27 August-1st September 2005, Skopje-Ohrid. Pavlovska, R., and Bozinovski, Lj., Z., “Reconstruction, Repairing, Enlargement and Building of another Storey of Existing Buildings Apartments in Skopje”, Proceeding of the First Congress of the Engineer’s Institution of Macedonia, Srtuga, Macedonia, Oktomber 24-26, 2002.
This page intentionally left blank
Enlargement of Balconies of Existing Residential Building “Karpos” in Skopje Kiril Gramatikov Civil Engineering Faculty, Skopje, F.Y.R. of Macedonia
Zivko Ljube Bozinovski Institut of Earthquake Engineering and Engineering Seismology Skopje, F.Y.R. of Macedonia
ABSTRACT: For the needs of the occupants, enlargement of balkonies of the existing buildings in large panel structural system has been designed. The mass construction of balkonies on large panel systems initiates the need for design of stable structures. Their mass construction in seismically active regions increases the seismic risk, so that errors made in the design and construction might induce heavy consequences during strong earthquakes.
1 INTRODUCTION After the Second World War, the increase in population and hence in the demands for residential space especially in Europe, have given rise to an extensive development of prefabricated structural systems as a substitution for the traditional monolithically constructed elements. The main difference between the prefabricated and monolith structures is that the prefabricated structures consist of elements that are cast in place different than the final position of the element in the structure. The elements constituting the structure are produced in factories from hence they are transported to construction site, mounted and connected by horizontal and vertical joints into an integral whole. The structural configuration for resistance against vertical and horizontal loads consists of structural walls, frames formed of beams and columns and systems consisting of interconnected walls and frames. Available is a wide range of prefabricated reinforced concrete structural elements like concrete blocks, beams and columns up to complete rooms or buildings known as "box" units. In the beginning, prefabricated elements were developed in non-seismically active regions and for low-rise structures of up to five storeys. The development of the technology of production and assemblage enabled development of these systems which became applicable also in the seismically active regions in Europe, North America, South America and Japan. Today, prefabricated buildings with a height of ten to twenty stories are frequently found in seismically active regions of many countries all over the world. Applied are three levels of industrialization: structures with prefabricated floor and roof structures and monolith bearing walls, prefabricated floor, roof and wall panels and finishing works performed in a traditional way, and prefabricated floor, roof and wall panels with finishing works (most or all) performed in factory using industrialized methods.
Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
92
Enlargement of Balconies of Existing Residential Building “Karpos” in Skopje
The present level of development of technology for analysis, production and assembling enables design and construction of prefabricated large panel reinforced concrete structural systems in seismically active regions. Modern large panel precast systems are cheaper than the traditionally constructed monolith systems, which depends on the economy in the processs of design, assembling and casting in place, the organization of the technological process, the amount of finishing works, the concentration and the amount of construction. The mass construction of large panel systems initiates the need for design of stable and economic systems. Their mass construction in seismically active regions increases the seismic risk, so that errors made in the design and construction might induce heavy consequences during strong earthquakes. The stability of these buildings depends on: the production technology, the way of connecting the structural elements, the composition of the elements, the reinforcement, the configuration of the contact areas of elements and the system of joints. The behaviour of the prefabricated large panel reinforced concrete systems depends on the behaviour of their constituent elements - vertical wall panels, horizontal panel slabs, vertical and horizontal connections. So far, during the design and analysis of large panel systems under static and dynamic loads, the vertical wall panels have been considered to behave in elastic range. They are designed with identical proportions and reinforcement distributed along the height of the building. They are reinforced by a relatively high pecentage of vertical and horizontal reinforcement, often with a non-controlled mechanism of behaviour up to ultimate states of strength and deformability. The vertical and the horizontal joints are considered to behave in the nonlinear range, most of the total energy being dissipated through them. After the occurred earthquakes, cracks and damages in the vertical wall panels have been observed which means that they suffer nonlinear deformations and damages due to the complex stresses induced by moderate and strong earthquakes. Diagonal caracks have not been observed. The same has been proved by the results of experimental investigations of fragments of large panel systems. 2 GENERAL DESCRIPTION Large-panel system "KARPOS" The large-panel precast system "KARPOS" represents modified Soviet system which has been especially designed for the needs in Skopje. The structural system consists of bearing vertical, central and facade reinforced-concrete wall panels supporting the floor panel slabs. The panels are interconnected by vertical and horizontal wet joints filled with cast-in-place concrete (Fig. 1-6) The system is applied in buildings with a height of 4-5 soreys, whereas the theoretical and experimental investigations were done for a building with 9 storeys.
Enlargement of Balconies of Existing Residential Building “Karpos” in Skopje
93
Figure 1. Site plan of tyipical residential unit, "KARPOS" system - Skopje
STREET "ILINDENSKA"
C
C
C
SERVICE STREET
A
A
B
A
B
P
B
P
P
B A
P
A
P
B
INTERNAL STREET
B
INTERNAL STREET
B
A
P
A
A SERVICE STREET
SITE PLAN OF TYPICAL RESIDENTAL UNIT 0
10
20
30
M 1:2000
40 50m
NS.2
NS.2
NS.2 VS.1-2
NS.1
NS.3
NS.2
NS.1
VP.6
VP.3
VS.1-2A
NS.4
VS.6
VS.1-2A
VS.6
VS.1
NS.4-2 NS.3-6
VP.6
NS.3-6
VP.2
VS.2
VP.1
VP.2
VP.5
VS.7A
15
VS.6
P=8.00m2
VS.1-2
VS.1-3 VS.1-2A
VP.6
VP.3
VP.4
VS.9 EK.1
VS.3A
VP.1
VP.6
VP.3
VS.2
VP.1
VP.2
VS.4A
VS.1-2A
VS.1-2A
P=16.18m2
NS.4-2
VP.2
P=3.48m2
VS.6
VP.1
NS.3-6 576
VS.4A
VS.3A
P=6.00m2
VP.3
VP.7
VP.2
VP.4 EK.1 VS.9
VS.1-2
VP.5
B1 -
VS.3A
VP.5
VP.2 VS.4A
VP.5
VP.7
P=17.16m2
320
1
NS.2 320
2
NS.3-2 260
3
--
19
1
NS.1
90
A
NS.1
VS.1-2A
VS.1-2
VS.1
NS.4
C NS.3-6
576 1182 1152
B
NS.3
VS.1
NS.2
VS.1
B -
NS.1
VS.1
A -
15
C
90
1
--
Figure 2. Characteristic floor plan of the "KARPOS" system - Skopje
NS.2 320
4
NS.1
NS.2
320
5
320
6 0
NS.1
320 3400 3438
1
7 2
3
4
5m
NS.2 320
8
NS.3-2 260
9
NS.2 320
10
NS.1 320
11
180
19
12
FLOOR PLAN
94
Enlargement of Balconies of Existing Residential Building “Karpos” in Skopje
Figure 3. Characteristic floor plan of the "KARPOS" system – Skopje
F - BP1-3
10.72
BP-1 NS3-3
PR-1
+8.10
BP-1
D -
NS3-3 +6.75
LM-1
+5.40
NS3-3 +4.05
LM-1
5.32
+2.70
NS-5 +1.35
±0.00
NS-3
-0.08
BP1-3
BC15
-1.01
NS-7
LM-2 -2.17
A
BP1-3
PR-2
NS3-2 -1.23
BP1-3 NS-3
2.62
LM-1
LM-1
BP1-3
E -
NS-3
PR-2
LM-1
BP-1
BP-2
8.02 PR-2
LM-1
BP-1
NS-3
-2.17
B
576 0
1
C
576 3
2
SECTION
5m
4
Figure 4. Joints of the "KARPOS" system – Skopje, b) vertical joint EXTERNAL R.C. PANEL
EXTERNAL R.C. PANEL
6 5 25
15
DETAIL "A"
14
SEALANT
10
SEALANT
INSITU CONCRETE
EXTERNAL R.C. PANEL
INSITU CONCRETE
INSULATION 6cm
DETAIL "B,B1" 12-14 INSULATION 6cm
INTERNAL R.C. PANEL
INSULATION 1.5cm
EXTERNAL R.C. PANEL
SEALANT INSITU CONCRETE
DETAIL "C" 19
6
Enlargement of Balconies of Existing Residential Building “Karpos” in Skopje
95
Figure 5. Joints of the "KARPOS" system - Skopje EXISTING BITUMEN COVER
ZINC COVERING SHEET
DETAIL "F"
EXTERNAL R.C. PANEL
INSOLATION 6cm
R.C. FLOOR PANEL 10cm
25
BALCON
ROOM EXISTING FLOOR (PARQUET)
EXTERNAL R.C. PANEL
SEALANT
EXISTING FLOOR (TERATZO) INSITU CONCRETE
R.C. FLOOR PANEL 10cm
R.C. BALCONE PANEL 10cm
DETAIL "D" 90
EXTERNAL R.C. PANEL
SEALANT
DETAIL "E" 19
6
6
19
Figure 6. Enlargement of balconies on LPS transformed into residential areas
60
96
Enlargement of Balconies of Existing Residential Building “Karpos” in Skopje
The existing building structures usually consists of a basement, a ground floor and two to three storeys. The bearing structure of the building consists of bearing RC walls in both orthogonal directions. The floor structures consist of reinforced concrete slabs with a thickness d=15.0 [cm]. The structure is founded on RC strip foundation. The roof structure also represents a RC floor surmounted by a plane terraces or timber roof structure. For the needs of the occupants, enlargement of balconies has been designed. 3 PROBLEM CONCERNING STRUCTURE 3.1. Problems a) Damages Due to the ravages of time, improper maintenance and design/performance defects in the course of time, have suffered different extent of damage and require proper maintenance. b) Interventions The interventions being done on this old residential buildings involve enlargement of balconies that are transformed into built residential areas and building of residential attic. 3.2. Actions a) Loads Vertical – Gravity and Live Loads Horizontal – Wind Load Exceptional Loads Earthquakes b) Actions Age of structures Intervention on structures Adding on the side of buildings (balconies, galleries, rooms) Maintenance 3.4. Solutions 3.4.1. Strategy for improvement Repair of damaged structures Revitalization of the existing structures
Enlargement of Balconies of Existing Residential Building “Karpos” in Skopje
97
4 CONCLUSIONS The behaviour of the prefabricated large panel reinforced concrete systems depends on the behaviour of their constituent elements - vertical wall panels, horizontal panel slabs, vertical and horizontal connections. During the design and analysis of large panel systems under static and dynamic loads, the vertical wall panels have been considered to behave in elastic range. They are designed with identical proportions and reinforcement distributed along the height of the building. They are reinforced by a relatively high pecentage of vertical and horizontal reinforcement, often with a non-controlled mechanism of behaviour up to ultimate states of strength and deformability. The vertical and the horizontal joints are considered to behave in the nonlinear range, most of the total energy being dissipated through them. After the occurred earthquakes, cracks and damages in the vertical wall panels have been observed which means that they suffer nonlinear deformations and damages due to the complex stresses induced by moderate and strong earthquakes. Diagonal caracks have not been observed. The same has been proved by the results of experimental investigations of fragments of large panel systems. From structural aspects, analysis of the stability of existing structure was made. The results show that capaciti of strength and deformabiliti are great than required by Code.
5 REFERENCES Bozinovski, Lj., Z., “Improving The Quality Of Existing Urban Building Envelopes”, EE-21C, International Conference on Earthquake Engineering, 27 August-1st September 2005, Skopje-Ohrid. Pavlovska, R., and Bozinovski, Lj., Z., “Reconstruction, Repairing, Enlargement and Building of another Storey of Existing Buildings Apartments in Skopje”, Proceeding of the First Congress of the Engineer’s Institution of Macedonia, Srtuga, Macedonia, Oktomber 24-26, 2002.
This page intentionally left blank
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope – Malta Ruben Paul Borg Faculty of Architecture and Civil Engineering, University of Malta, Malta
ABSTRACT: This paper discusses adaptations and alterations in existing buildings, extension and construction of additional floors, and repair of housing development in Malta. These issues become particularly relevant in the case of Malta as an Island State, in view of the limited availability of land for the construction of new residential buildings, and resources. The structural alterations and improvements carried out in existing buildings, and the construction of additional floors are presented with direct reference to typical load bearing masonry structures.
1 INTRODUCTION Land availability for development is diminishing particularly due to Malta’s small size and the limited land resource, and the tight land development and planning policies. In Malta today, we see a shift from the former single plot owner, developer and user scene into a new scenario, where due to increase in land costs and reduced availability of land, contractor-developer partnerships are forming to build smaller units to maximize land use & profits, now being sold as apartments in the free-end open property market. Changing planning legislation is also leading to increased building height limitations, in existing and new development areas. With this scarcity of land, new trends in residential development are emerging, mainly concerned with either the redevelopment of housing stock into smaller units, or the upgrading of existing buildings. The first approach in residential development, concerns the reconstruction of existing residential buildings into smaller units. Old and even relatively new terraced houses, built during the past thirty years are being sold to entrepreneurs for demolition and redevelopment into apartment blocks with smaller residential units for today’s reality of smaller families, and also in line with the general demand for smaller affordable units. The second approach in residential development, concerns the adaptation and upgrading of existing residential development in order to accommodate modified or new habitable spaces, either as extensions to the residential units, or as new residential units within the building. The following main action is normally implemented: Refurbishment and repair of the existing apartment block. Alterations to the existing residential units in order to accommodate an increased number of units. Construction of additional floors over the existing apartment blocks. These interventions are normally implemented either separately or together, in the overall upgrading of the residential block. Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
100
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
Figure 1. The construction of additional floors onto existing residential buildings.
Figure 2. The renovation and construction of additional floors onto existing buildings.
2 GENERAL DESCRIPTION OF THE STRUCTURE. The typical housing development discussed in this paper, consists of terraced houses and apartments constructed during the past thirty years. The main housing typologies consist of two storey terraced houses, and apartment blocks of two or more floors. In general apartment blocks are built in a row, or free standing with a surrounding public space. The structural system normally adopted in the construction of residential buildings in Malta consists of load bearing masonry structures. Upgrading and improvement of the building envelope is normally required in view of the following: Reduced availability of space, high price of land, and possibility of extension of buildings by the construction of additional floors. The inadequacy of the residential typologies in relation to the present needs of the users. The presence of serious building defects due to the application of inferior construction materials during construction. Low quality of building services and / or their performance in relation to the building layout. Lack of ventilation and humidity in the internal spaces, water penetration, inadequate detailing. Inappropriate maintenance of the building structure. In view of the above, various interventions of repair, upgrading and alterations to the existing structure, and construction of additional floors overlying the existing structure are required. 3 PROBLEMS CONCERNING THE STRUCTURE. 3.1 Typology of the Structure The structural solution adopted in the construction of residential buildings normally consists of vertical load bearing walls, with the main structural elements being masonry block work, and the structural reinforced concrete slab, spanning onto the load bearing masonry walls at different levels. The reinforced concrete slabs are normally cast in situ slabs, with mesh reinforcement and reinforcement bars.
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
101
The material properties and dimensions of load bearing masonry elements vary. In particular the main elements used are concrete masonry blocks and quarried globigerina limestone blocks. External walls are generally constructed as cavity walls using globigerina limestone elements, with an approximate wall thickness varying from 375mm to 510mm. Concrete block work is also used in some cases, with a wall thickness of 230mm. Both concrete block work and limestone elements are used in the construction of internal load bearing walls. Wall thicknesses may vary, but the thicknesses normally adopted are 230mm, 180mm and 150mm. Reinforced concrete masonry block work is also used in the construction of load bearing masonry structures. The one way or two way spanning reinforced concrete slabs span onto load bearing walls. Spans vary according to the different spaces of the dwelling, with maximum spans normally in the range of 6m. Hollow concrete block work supported on parallel precast inverted T beams are also used in roof construction. In view of planning and other criteria, new residential development consists mainly of residential units in upper floors, overlying garages in the lower levels of the building. The layout of the load bearing structure of the residential units in the upper levels varies from that of the underlying garage level, and in general, larger spans and open spaces are required in the lower level. Reinforced concrete beams and slabs, and prestressed slabs, are generally used in the roof over the lower level, to transfer the loads of the overlying load bearing structure to the walls. 3.2 Problems Concerning Structure The required interventions for the upgrading of the building, are mainly associated with the deterioration of the structure and also the possibility of alterations and the addition of new floors. 3.2.1
Deterioration of the structure.
The main area of concern is associated with structural deficiencies and deterioration of the building structure. These are normally the result of construction materials of inferior quality that had been used originally during construction, inadequate detailing and lack of maintenance. Such deficiencies are normally common in the roof structure, external walls and services shafts, balconies and projections of the structure, and in the detailing between the reinforced concrete and masonry elements, and wall / roof joints. The main defects in the case of reinforced concrete roofs are normally related to inadequate cover to reinforcement, low grade of concrete used, inadequate detailing leading to water penetration, and eventual corrosion of reinforcement and spalling of the concrete . Defects in walls are normally a consequence of water penetration, inadequate construction and structural detailing, deficiencies in the foundations of the building, or inadequate interventions of structural alterations in lower levels of the building, causing arching action or other movements, and cracks in walls.
102
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
Figures 3. Water penetration into the Reinforced Concrete Roof structure.
3.2.2
Figure 4. Deterioration of Reinforced Concrete slab.
Alterations to the building
The various floors of the structure normally follow the same plan layout at each level. In the case of load bearing walls that are interrupted at any level, reinforced concrete and steel beams are required in order to transfer the load on to adjacent walls. The intervention for the formation of new openings may cause redistribution of the load within the structure, and may result in movements in the structure. The extent of damage caused by such interventions varies and depends on the methodology adopted. The problems associated with the planning of the units and the required optimization, have to be assessed in view of the possible adaptability of the various spaces, and structural constraints typical of load bearing construction. Reconstruction rather than alteration and adaptability of the building, may not be possible specifically due to third party ownership of upper or lower floors within the same building.
3.2.3
Construction of additional floors
Additional floors over existing structures are not normally built using a lightweight structure, but usually consist of a load bearing structure adopting masonry walls and reinforced concrete slabs. This is particularly directly associated with costs of building materials. Typical problems related to the construction of additional floors, are normally associated with the inadequate load carrying capacity of the existing structural elements. Various structural elements in the existing building, including reinforced concrete beams and slabs, were not intended to sustain the load of additional floors. The stress distribution in the load bearing walls has to be analysed with respect to the additional loading from the new floors. The requirement for improved spaces, including extensions to existing areas, and the creation of new units, has to be assessed against the structural requirements and limitations of the existing building, and also the properties of engineering materials used, both in the existing structure, and in the proposed extensions. The ground conditions and the adequacy of the foundations need to be analysed.
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
103
3.3 Strategy for Improvements The intervention on the existing building is intended primarily to improve living conditions, to satisfy the necessities of the residents, and the quality of the spaces in general. To achieve these goals, it is required to: Improve the architectural quality of the building, and improve the general layout and disposition of residential units Improve the performance of the building and structure, while complying with standard recommendations. 3.4 Actions The main interventions for the renovation of the building, are set out, with the following objectives: To assess and preserve the general stability requirements of the structure. To assess the extent of decay and deterioration on the existing structure, and consequently identify the structural elements that will either be substituted, or repaired. To assess the direct and indirect implications of the extension and alteration interventions, on various parts of the structure and sub structure. To implement the necessary measures, for the general upgrading and renovation of the building, including the accommodation of lifts within the building where these are not present. 3.5 General Description of the Works and Critical Evaluation In the repair and structural upgrading of an existing structure, it is important to carry out an appraisal of the extent of the intervention, and type of intervention required, viability in view of the present state of the building, its age, intended other interventions that need to be carried out, and the general improvement of building conditions. Possible reconstruction of the structure, or parts of it have to be considered in relation to third party properties within the building, and the feasibility and viability of the project. The main actions concerning structural interventions are the following: Deterioration of structural elements. Alterations to the existing structure. Addition of floors onto the existing structure. 3.5.1
Deterioration of structural elements
In the case of deteriorated reinforced concrete elements, the level of damage is assessed, in order to define the extent of repair and/or replacement of structural elements that is required. The quality of the materials is assessed with respect to the expected performance of the structural elements and standard recommendations. In the case of the repair of reinforced concrete elements, all agents causing deterioration, have to be eliminated and adequate detailing is envisaged. In the case of water penetration, the structure must be rendered waterproof. The reinforced concrete roof structure is repaired using proprietary systems for the repair of reinforced concrete structures.
104
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
Strengthening of structural elements using FRP (Fibre Reinforced Polymer) or other techniques, depends on the quality of the material and extent of damage, the required performance and standard requirements. General testing including also non destructive testing of the materials, and structural monitoring, normally provide important data for analysis. Strengthening of under-designed structural elements, particularly reinforced concrete slabs, is also implemented by the introduction of intermediate support/s, possibly steel beams, FRP and other techniques.
3.5.2
Alterations to the existing structure.
Various alteration works in buildings are related to a desirable improved layout of the residential units, needs of the users and the introduction of new services. The possible intervention is assessed in view of the structural implications within the existing building. Therefore an understanding of the structure is required, together with a thorough assessment of possible third party properties within the building or adjacent spaces. In general the extent and type of alterations that can be effected depend on the structural layout, load transfer possibilities, and any constraints present that can include structural disposition and internal service shafts, and yards. The methodology adopted in alteration works is based on the techniques adopted as outlined in the following: Assessment of ground conditions and adequacy of the foundations of the existing building. Assessment of loads, including allowance for the construction of new levels. Introduction of specific structural elements that can include reinforced concrete beams, and steel beams for new openings. Formation of openings using a single beam system or a double beam system, in view of the construction methodology adopted. Introduction of new structural elements that are only required during the execution of the works. Temporary support of the overlying structure. Adequate detailing of joints. Construction of lift shafts and new service shafts to accommodate new services, for the general upgrading of facilities in the building, and with an allowance for future extensions. The following are particularly relevant in the execution of alteration works in an existing building: Assessment of movements and arching action in load bearing walls, particularly in the case of underlying wide openings. Evaluation of the implications of the intervention on the finishes, that can include damages to wall and floor finishes, in overlying or adjacent spaces and third party properties.
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
105
Figures 5 & 6. Internal alterations and the formation of openings within existing buildings.
3.5.3
Addition of floors onto the existing structure
There are two typical general cases for consideration. The first case concerns relatively recent residential buildings, where in view of predictable and projected relaxation of building height limitations, the structure of the existing building, had been designed and constructed to accommodate the already planned new overlying structure. In this case, the structure of the existing building is designed to accommodate the layout of additional load bearing floors, and to transfer effectively the loads. The second case concerns existing buildings, where the structure was not intended to carry the additional load resulting from the new floors. The ground conditions and the adequacy of the foundations of the existing building have to be assessed. An appraisal of the load carrying capacity and load distribution through the existing structure, and an analysis of structural elements within the existing structure, are also conducted in view of the proposed construction of additional floors.
The feasibility of the project, and the approach taken depend primarily on the outcome of the assessment of the existing building conducted. In order to sustain the additional loads, the existing structure and the foundations can be strengthened, and new structural elements can be introduced in the underlying existing building. Due to the implications of the construction of additional floors onto existing buildings, the following criteria are normally taken into consideration: The adoption of a new layout for the overlying floors results in a new load bearing structure with walls that do not coincide with the underlying walls. The existing roof of the building can be replaced with a new structure intended to accommodate the new plan layout, and transfer the load to the load bearing walls. Independent transfer structures in the form of steel or reinforced concrete beams cast beneath the new walls or floor slabs, supported onto the underlying walls, can transfer the load of the additional floors to the existing structure below. The load transfer structure is normally designed to transfer the load directly to the load bearing walls of the existing structure, reaching the foundations.
106
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
The construction of the additional floor/s, requires the evaluation of the building layout in the underlying levels. The layout of the proposed levels can be optimized, in view of the structural solution for the transfer structure, yet without compromising the functional and planning requirements. Appraisal of the ground conditions and adequacy of the building foundations. Analysis of load carrying capacity and load distribution through the existing structure. Possible strengthening of the foundations and the existing structure Reduction of the load of the overlying structure is achieved by using lighter materials particularly concrete block work rather than limestone blocks, and through the use of lightweight concrete block work for internal non load bearing partitions. When considering the construction of additional floors over existing residential buildings, the following have to be addressed also: The architectural identity of the building and the implications of the additional floors not only on the building itself but also on the streetscape. In view of planning constraints and requirements, the building facade of additional floors at specific levels must be receded back from the façade of the underlying building. Beams are required to transfer the load. Sanitary regulations establish the size of back yards and internal yards, and lead to receded floors in the upper levels. Beams are introduced to transfer the load.
Figure 7 & 8. The construction of new floors onto an existing building.
Figures 9 & 10. The construction of a reinforced concrete Transfer Structure.
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
Figures 11 & 12. Construction of floors receded back from the front and back façades of the building.
ROOF
LEVEL 6
LEVEL 5
LEVEL 4
LEVEL 3
LEVEL 2
LEVEL 1
LEVEL 0
Figure 13. Residential Development: Longitudinal Section.
107
108
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
A
A
BEDROOM 3
BEDROOM 3
BEDROOM 2
BEDROOM 3
BEDROOM 2
BEDROOM 2
BEDROOM 2
BOX
BOX
LIFT
LIFT BOX
BATH ROOM
BOX
BATH ROOM
BATH ROOM
B
B KITCHEN
BEDROOM 3
B
BATH ROOM
ENS
B
HALL SITTING ROOM ENS
MAIN BEDROOM
SITTING ROOM
SITTING ROOM
ENS
KITCHEN
SITTING/ DINING
LEVEL3
MAIN BEDROOM
BEDROOM 3
KITCHEN
KITCHEN/ DINING
MAIN BEDROOM
A
LEVEL 4
Figure 14. Residential Development: Plans of typical floor, and receded overlying floor.
Figure 15. Residential Development: Upper floors receded from the building facade.
A
Techniques of Structural Alterations and Improvements in Relation to the Urban Building Envelope
109
4 CONCLUSIONS. The reconstruction or upgrading interventions of the existing residential building is to be assessed in view of various important factors, namely the state and age of the building, needs and project viability. Adaptation works are normally promoted particularly in the case of the presence of third party ownership of parts of the property, when as a consequence, reconstruction of the building is not possible. This is frequently the case in Malta also because of the high occurrence of home ownerships. Possible improvements in the renovation, maintenance and extension strategy of existing residential buildings include the proper assessment and understanding of the structural system, use of lightweight materials in extensions and additional floors, adequate detailing and improved techniques in repair, for better durability. The need of frequent future interventions is reduced. In the case of new load bearing residential development, the structure is designed in view of anticipated possible future extensions, and additional floors. Reinforced concrete beams are also incorporated in the different levels of the structure in critical location, where it is anticipated that openings will be formed due to functional requirements and changing lifestyles. The availability and present relative price of particular construction materials in Malta, namely quarried limestone, concrete brickwork and reinforced concrete lead to the adoption of specific construction techniques and methodologies in extension works and construction in general. The limited availability of land for construction, the high costs of land, and development planning constraints and regulations, set the scenario for the current trend in the upgrading and extensions to existing buildings as presented in this paper. 5 REFERENCES Aquilina K. 1999, Development Planning Legislation, The Maltese Experience; Malta BICC, 2000, Housing Affordability in Malta, Malta.
This page intentionally left blank
Adding an Extra Storey J. Engelmark BYG.DTU, Dept. of Civil Engineering, DTU, Technical University of Denmark
T. Dahl & E. Melgaard The Royal Danish Academy of Fine Arts, School of Architecture
ABSTRACT: The bigger part of multi-storey apartment buildings in Denmark from the period 1960-80 were fitted with flat roofs covered with asphalt felt. The construction of these roofs and the quality of the asphalt felt used were in general not adequately tested prior to be used, and therefore the majority of them had to be renovated after a shorter period. In stead of just replacing the original roof with a new one, it is now a days rather common to ad an extra storey where that is possible according to local planning. The reason is as a rule based on economical benefits, but very often this extra storey also gives a lift in the architectural appearance of the building. This case has been chosen because the combination of the two seems to be fulfilled.
1 GENERAL DESCRIPTION OF THE CASE STORY The case studied is one of many. It is chosen because of the very simple way of handling the problem with leaking roofs in the newer part of the housing stock being built with flat roofs. Another reason is that the original buildings involved are some of the very early examples of the most common way of building prefabricated RC-panel multi-storey apartment buildings in Denmark – the type with slabs spanning between load bearing transverse walls and with nonload bearing facades. The estate is situated west of and nearby central Copenhagen in the commune of Rødovre – a suburb now fully developed; a development that started before, but accelerated after World War 2, and was fulfilled less than half a century later. The estate is corporate owned and consists of 2 blocks 4 stories high, respectively one block 8 stories high, and with a total of around 800 apartments (Fig. 1). The size of the apartments are either 3 or 4 rooms, with a gross area of app. 70 respectively 84 m2 (exclusive staircase- and balcony areas) and originally designed for families of 4 to 6 members (Fig. 2). The combination of the uniform size and lay-out of the existing apartments, the poor (original) heat insulation on top of the buildings and the need of maintenance of the roofs, and also the fact that practically no more building sites were available in the commune, gave the background for adding an extra storey on top of the buildings. Some years ahead of the adding of the extra storey’s, the facades were extra insulated. The problems arising from the original uniform appearance were then coped with by a very colour full facing – but not with the same success as the later adding of storey’s. The extra storey on the 3 blocks gave all together 73 new apartments. Of these apartments 21 are very small – 25 m2– and designed/reserved for youngsters. The rest are of a size – 60 to 72 m2, all exclusive access- and balcony areas – and of a standard designed/reserved for now a days families of 2-3 persons or singles. The project was carried out in the early 1990’s. Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
112
Adding an Extra Storey
Figure 1. Arial view seen from Northwest of the estate after adding of the extra storeys. The longest block is 180 meter long and the shortest 120 meter (ref. Project, Oct. 1990).
2 PROBLEM CONCERNING STRUCTURE
2.1 Typology of structures The existing buildings are made from prefabricated concrete slabs/panels – the slabs being 1,2 meters wide and having spans of 2,4/3,6/4,8 meters in between transverse load-bearing panels. The panels – also providing stability transverse – are 1,2/2,4 meters wide and with a height of app. 2,6 meters, respecting demands in the building code of 2,5 meters free room-height and allowing space for the typical Danish floor construction in housing: a 10 cm thick raised wooden floor. Stability lengthwise is provided only with spine walls in connection with the staircases. The dimensions of slabs (partly hollow and 18,5 cm thick) and transverse panels (massive and 15 cm thick) are not originally and final determined by loads – they are far too heavy in general – but for reasons of fulfilling demands to sound- and/or fire insulation in between the apartments. Opposite to this the spine walls in connection with staircases are of a greater thickness (18 cm) and also pre-stressed cable-connected to basement walls cast in situ to secure stability lengthwise. All in all the structure of these buildings are more than able to take up the additional load from an extra storey (Fig. 2 and 3). The facades were fitted with new window-panes and the opaque parts extra-insulated in the late 1980’s just by providing an extra layer of mineral wool covered with corrugated steel plates in a many-colored way – being hottest fashion at that time to avoid the overall grey look.
Adding an Extra Storey
113
Figure 2. Typical lay-out of a staircase section in the existing buildings with 2 3 room apartments pr. storey. Staircase facing east (ref. Archive material).
2.2 Problems Danish multi-storey apartment buildings from the period after 1960 and on, were very often fitted with a flat roof – a so called built-up construction: 2(3) layers of asphalt-felt laid on top of an almost horizontal wooden boarding on rafters supported by the finishing RCslabs, and with just the amount of heat-insulation required at that time: 10 cm mineral wool placed between the rafters This kind of construction with the quality of asphalt-felt obtainable at that time, showed very quickly not to be able to withstand a climate like the Danish. So reparations had to be done very often, and as a rule just partly, where and when problems a raised.
2.3 Actions With the heavy rise in price on energy in the following decades an additional reason for a complete exchange of the roofs came up. And soon after the idea of adding an extra storey when making such rather big interventions was launched. The idea was of cause nearby: partly because the extra square meters would be relatively cheap to establish, and partly because of the more apartments to share the expenses following from not only making the new roof, but also running costs in general.
2.4 Description of works The new extra stories in this case can be described as terrace houses, but with access from balconies running in the whole length of the buildings. In each block every third of the existing staircases have been extended to the level of a new access balcony, which also is served by just one lift pr. block.
114
Adding an Extra Storey
Figure 3. West façade of a 4 storey block after adding of the new storey and lay-out of the new extra storey. Kitchen/living room situated to West (ref. Archive material).
As the blocks are situated with the facades pointing towards west and east, the new added extra stories take advantage of this situation by placing the combined living room/kitchen towards west and with the façade fully glazed to a rather spacious balcony. Furthermore the roofs slope gently from west to east with the maximum height to the west, which gives an extra spacious feeling and underlines the design of the new apartments. Bedrooms are placed to the east, where the existence of the access balcony (naturally) is a limiting factor to the number and size of windows (Fig. 4 and 5). The extra stories were build in units on the ground in a simple moveable field-factory (just a temporary kind of tent construction) placed at the parking areas situated up to the buildings. The units were then lifted in place by crane – each unit being as big as the single apartment (the biggest: 10 by 7,2 meters and with a weight of 22 tons). On top of the buildings the units are supported on 3 lines of I-shaped rolled steel beams, resting on small columns of the same material and anchored to the transverse panels underneath. It should be noticed, that the existing roof covering incl. the original insulation otherwise is kept partly because the existing roof covering acts as a waterproof layer in case of leaks in the installations, partly because the effect of the existing insulation and also of cause the expenses saved by doing so. The outer beams are only supported on every second panel, the centre beams supported on every, and the centre beams are therefore of a smaller size. This gives possibility for the existing as well as the new installations to run in all directions in the crawl space established this way between the existing roof and the floor of the new storey.
Adding an Extra Storey
115
Figure 4. Cross section West-East of new storey (ref. Archive material).
The balconies on each side are made of prefabricated reinforced concrete slabs with built-in slope and gutter, and placed on special made steel consoles which are supported and anchored like the beams (Fig.5). The construction of these units is directly comparable to the construction of a light-weight one-family house, as it has been and still is being build in Denmark – except that use of wood in the majority of the one-family houses would be preferred to steel in the load-bearing constructions, and that the external cladding almost always would be brickwork. The one-family house would also as a rule be fitted with a hipped roof. Studs, beams and rafters in walls, floors and roofs of the units are thin-walled steel profiles placed in a distance of 30 cm. and with dimensions in material and profiles according to span and load. The heat insulation placed in between these construction elements is mineral wool with a thickness of 15, 20 and 5 cm respectively in walls, roof and floor – the less insulation in the floor as a result of the crawl space underneath and the existence of the original (poor) insulation (Fig.5). Beams and rafters in floor and roof construction are sided by corrugated steel plates on which a wooden floor respectively the roof covering (asphalt-felt) is mounted. The underside of roof and floor is covered with one respectively 2 layers of plasterboard mounted on smaller thin-walled steel profiles supported by rafters and beams. The external walls facing the access balcony have an outside cladding of aluminum in shape of cassettes on wind-tight plasterboard. The inside is one layer of plasterboard. The external wall to the west is a wooden construction and fully glazed. Internal walls in the apartments are not load bearing (the roof spans from façade to
façade) and made from studs of thin-walled steel profiles with siding of plasterboard. The walls in between the apartments are made likewise, but as double constructions: first of all because of demands to sound as well as fire insulation (therefore a little heavier and with the necessary filling of mineral wool), next supporting and resulting in the choice of building technique: prefabrication on the ground as apartment-big units. The bathrooms floors and walls have of cause a waterproof finishing layer: ceramic tiles.
116
Adding an Extra Storey
Figure 5. Facades facing West and East of 4-storey respectively 8-storey block.
3
COMMENTS
Almost all of these concrete panel buildings are originally fit with a flat roof, and very often one wish for some kind of finishing of the buildings in height – a problem of aesthetics only, as it now a day is possible to construct an almost horizontal roof being both water proof and lasting. But – fitted with an extra storey – these buildings are in general gaining “that extra” which make the visual impression much better. And in the case studied this has been done in a very delicate way. The rooms in apartments having access by balconies and facing these have as a rule a problem in privacy because the windows are pointing to this “traffic area”. But in a case like this, where the apartments are the top ones, one could ask for a solution with use of skylights as a supplement and also because of the size of the eaves – not just for the rooms facing the access balcony; also the kitchens placed near the centre of the apartments would be far better of with the existence of (extra) daylight. The bathrooms being without daylight at all would of cause also benefit from having skylights. In the late 1980’s only few additions of extra stories in the newer part of the Danish housing stock had taken place. So the case studied is one of the first of its kind. Now a days – less than two decades later – a lot of such additions have been made, and often in a semi-industrialized way, like the case studied. The newest trend is a total prefabrication of such units – they arrive at the building site all factory-made and fully equipped (Fig. 6). Of cause there are limits to the size of such units when transported by train or truck – limits that seem to call for smaller parts easily assembled at the building site, either on ground or on the permanent place. Adding an extra storey to an existing building is not something new. In former time this was often done in need of additional space, but without the possibility of obtaining this because of lack of ground – examples on this could be fortified towns.
Adding an Extra Storey
117
Figure 6. One of the newer full-scale prefabricated solution in adding an extra storey. From an outdoor exhibition in Copenhagen 2005: the containers are to substitute an existing building.
Copenhagen being such a town until around 1850 has a lot of examples of added extra stories. In fact up around 1/3 of the buildings in the old part of town were fitted with an extra or two extra stories in the period up to the time, when the town was abandoned as a fortress, and the former demarcation areas around were allowed to be build on. In those days the authorities also used the adding of an extra storey as a means to modernize the building stock: a condition for permitting an extra storey on buildings already fulfilling the maximum profile legally allowed was e.g. to replace an existing half-bricked façade or gable wit a fully bricked one to upgrade for fire resistance. At that time no questions were asked to whether the buildings were able to carry the extra load – that was considered as a problem of the owners.
REFERENCES Project, October 1990, Architect R. Schmidt Archive material, Municipal Authority of Rødovre Commune, Dept. of Techniques Interview with the architect in charge, July 2005 Engelmark, J., 2005, The Future Use of the Existing Housing Stock. In Final Report: The Outcome of the Cooperative Activities, COST Action C-12. Leiden: Balkema Nationalmuseet, 1972, Historiske huse I det gamle København. København: Nationalmuseet
This page intentionally left blank
New Facade Combined With Inside Rebuilding J. Engelmark BYG.DTU, Dept. of Civil Engineering, DTU, Technical University of Denmark
T. Dahl & E. Melgaard The Royal Danish Academy of Fine Arts, School of Architecture
ABSTRACT: The case study deals with problems concerning bringing up existing buildings to present days standard of housing design – expressed more specific: the renewing of bathrooms and kitchens in the more traditional built part of the existing stock of multi-storey housing in Denmark. The solution in this case is a complete substitution of a part of the original building. The new part being a reinforced concrete construction made entirely of large prefabricated elements, including fully fit bathroom-units and closed by a curtain-wall. The case should be seen as an example more than the “final solution” – as a radical way to tackle problems in general, not being locked by standards of doing.
1 GENERAL DESCRIPTION OF THE CASE STUDY In an area in the central part of Copenhagen – in the commune of Frederiksberg –another and non-traditional way of bringing up the sanitary and living standard of the older part of the existing multi-storey housing stock has been tested. In buildings from the turn of the former century the original lack of bathrooms and often smaller size of kitchens, as well as heir usability and organization compared to the standard of present days, has been dealt with carrying out an experiment using modern building technology in renewal. The actual building dates back to the end of the 19th century, but the majority of multi storey apartment buildings were in principle build the same way till the mid 1950’s. The example gives a hint of possible alternative ways of looking at and handling with the existing housing stock, not just as objects to preserve – being as original in exterior as well as in interior as possible – but as existing structures being part of new ones. Or in other words: One could see at and act in handling existing buildings as comparable to “building sites in 3 dimensions”. In the actual case, bathrooms and modern, better equipped kitchens were established by removing a rather big part of the existing construction towards the court yard, and filling the hole with a new structure containing baths and kitchens and with a new facade projecting out in the backyard (Fig. 1, 2 and 3). The new load bearing structure is all made by just assembling pre cast reinforced concrete elements at site as done in any new building, and the new façade likewise. The biggest element being a double bathroom unit and the smallest a facade column. The case presented is one of five almost identical projects in the same area. All projects with the same consultants as well as contractor, and carried out at the same time. Otherwise it was calculated, that there might not be an economical stable base for the experiment. The projects were carried out in the very first years of this century. Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
120
New Facade Combined With Inside Rebuilding
Figure 1. Façade to the courtyard before and after (ref. Archive material).
Figure 2. The lay-out of apartments before and after (ref. Archive material).
2 PROBLEM CONCERNING STRUCTURE 2.1 Typology of structures Before the introduction of pre cast, reinforced concrete as the dominant load bearing building material in multi-storey housing in Denmark, brickwork was not only the natural choice, but also the only allowed by law according to reasons of fire safety in such buildings. In general buildings like these would be furnished with a floor construction of wooden beams spanning in between the facades and a spine wall, but with beams of iron sustituting the wooden ones where the construction of either balconies or bay-windows called for a stronger or more fire-resistant material. Also the constructions of bathroom floors were dependant on the use of iron beams, as a water resistant construction only was possible to obtain with concrete, and as the walls surrounding bathrooms as a rule would be of a non-load bearing type.
New Facade Combined With Inside Rebuilding
121
Figure 3. Cross section of the building before and after (ref Archive material).
2.2 Problems The existence of bathrooms in the lay-out of ordinary multi-storey housing started to be standard from the 1920’s – first in the bigger apartments and just a decade later as standard in all. The typical floor construction in bathrooms from that time and up to the 1950’s was made as described above and with a topping of terrazzo. The surrounding light-weight walls being of a non-organic material, e.g. different kinds of cement based relatively big blocks bricked up with reinforcement of iron in the joints and with a cladding of ceramic tiles. The services - down-pipes, pipes for domestic cold and hot water and even sometimes pipes for central heating - was as a rule placed visible in the bathrooms and also serving the kitchen when possible. In general many of these services – being up to more than 80 years old – are worn out by now, and they call for renewal. But very often not only the services need to be replaced, also the floors are often damaged by water leaking into the construction and hereby corrugating the bearing iron beams to a degree, where replacement is needed to avoid collapse of the construction. The reason for this is partly because of the many pipes – often placed in corners – penetrating the floor and the bushings not being sufficient watertight, and partly because of the nature of the buildings construction as a whole, as it consists of a mixture of wooden and iron beams combined with brickwork as vertical load bearing. Renovating/rebuilding a bathroom on site is a very delicate job: It calls for the participation of nearly all crafts represented in the building sector and on a very small area, with likewise very limited possibilities of access, and also demands not to harm the surroundings. Even with the best design, the involving of the most skilled craftsmen, a planning of works and a logistic in delivery “second to none”, there are numerous chances for failure – quality assurance is in this situation almost impossible to carry out except in theory. What is described above is foreseeable to happen in the future also for the housing stock built in the first decades after World War 2.
122
New Facade Combined With Inside Rebuilding
Figure 4 and 5. A double bathroom unit being lifted from the street and up over the top of the building by a mobile crane.
2.3 Actions The answer to the problems listed could be prefabrication and to a scale where jobs on site are minimized. In new-building in Denmark the use of fully fixed bathroom units is almost standard. But in renovation and modernization of the older part of the housing stock, not originally fitted with bathrooms, the prefabrication of bathrooms has been limited to assembly of building parts – e.g. floor, walls and ceiling – and with the following accommodation done on site. The success of such initiatives have been limited over the years, and in general bathrooms in these buildings are totally made on site and with all the problems involved as described ahead. But lately another approach to problems has been tried out: Cutting a hole in the existing building and erecting a brand new structure right from the ground and up. Handling problems this way, the technology in new-building can be used even in refurbishment of the existing building stock. 2.4 Description of works In the actual case a very small number of elements were used: A double bathroom unit, an apartment division wall, 2 floor elements and 2 facade columns pr. storey. All together a fivestorey tower erected inside the existing building and with a floor area pr. storey of app. 20 m2. The bathroom unit being the biggest and heaviest: 3,5 by 1,6 meters and with storey-height – app. 2.8 meters – and a weight near to 10 tons. All elements were lifted and brought in place by a mobile crane situated in the street in front of the building. The elements were lifted over the roof of the five-storey building, and maneuvered in place by the crane operator via a camera on top of the jib. A very delicate job that might be interrupted by windy days (Fig. 4, 5, 6 and 8). The procedure of the jobs following was just
New Facade Combined With Inside Rebuilding
123
Figure 6 and 7. The double bathroom unit hanging high, ready to be lowered down in the rather big hole cut into the building.
as it could be seen at any building site handling contemporary buildings. The curtain wall being mounted likewise, thus only the new roof construction on top remains and the building is closed, ready to be furnished with the remaining finishing inside jobs. After the making of the hole in the existing building, and ahead of the fast assembling of the new structure, the in-situ making of the new foundations had taken place. At least the making of the hole and also the new foundations will always be of a nature difficult to prefabricate. Summing up: The result was an economical success, as the price for the renewing/modernization was equal to the price doing the same jobs the old-fashioned way. But on top was added a shorter total time of construction and therefor less money was spent on short-time loans as well as less money on tenant’s temporary accommodations. Another benefit was the resulting technical quality of especially the bathrooms, as they were delivered fully equipped and ready to use just by removing the provisional closing of the bathroom-door. 3 COMMENTS Criticism to this method is divided into – at least – two: One is that such at total new-built part inside an existing building is blocking for future inventions in a much more severe way, than the old-fashioned methods based on interfering as little as possible in the original construction. Whether these methods are crafts-man like or semi-industrialized, they offer better possibilities for future inventions – and one should foresee a future for buildings like these including not only one, but several renovations in the future. Another is that today’s attitude towards services in buildings is, that they should not be seen. So far the result of this attitude has been answered by using built-in systems of pipes of any kind, and of cause in bathroom-units to the ultimate limit. But it seems in general as if reparations or the probable more often renewal of services than other building parts is being severely ignored by doing so.
124
New Facade Combined With Inside Rebuilding
Figure 8. The bathroom unit maneuvered down and ready for final assembling.
Taking more radical measures such as partly rebuilding an existing structure involving the erection of a new load bearing one including a new facade to an older building, is not as remarkable as it might appear. In Copenhagen as well as in other cities in Denmark – and also in the majority of other European towns) the upgrading of the building stock through the centuries has involved a still bigger attention to fire safety. The original buildings of central Copenhagen were almost all originally constructed as halftimbered, and those of them surviving the 3 big fires, that have taken place in the past, were afterwards – and often with economical subsidies from the authorities – rebuilt partly to better withstand fire. First of all by replacing half-timbered gables to neighbors by solid brick-built ones, second by doing the same to facades of a like construction facing the streets and finally all remaining exterior walls.
REFERENCES Pålsson, K., Architects M.A.A. & Falkon, Engineers F.R.I., Project of May 1999. Municipal Authority of Frederiksberg Commune, Dept. of Techniques, Archive material. Engelmark, J., 1983, Københavns Etageboligbyggeri 1850-1900, Sbi-rapport 142. Hørsholm: SBI Engelmark, J., 2005, The Future Use of the Existing Housing Stock .In: Final Report on the Outcome of the Cooperative Activities, COST Action C-12. Leiden: Balkema
Reconstruction, Enlargement, Adding Storeys and Revitalization Zivko Ljube Bozinovski Institut of Earthquake Engineering and Engineering Seismology Skopje, F.Y.R. of Macedonia
Kiril Gramatikov Civil Engineering Faculty, Skopje, F.Y.R. of Macedonia
ABSTRACT: For the last two decades, intensive activities on reconstruction, repair as well as enlargement and building of other storeys on existing old residential buildings has been carried out.The reasons for such an extensive reconstruction and building of other storeys onto old residential structures is the increasing need of residential area, revitalization and repair of structures that are 30 to 50 years old as well as improvement of the quality of living of the occupants of those structures.
1 GENERAL DESCRIPTION The changes of political-economic conditions that took place after 1990 and the reduction of construction of big residential complexes and structures resulted in a need of residential area in Skopje. At the same time, the old buildings already had technical and infrastructure problems as were ruined facades, leaking roofs, inclination, cracks, weathered installations etc. To solve both problems of obtaining residential area and repairing old structures, these started to be repaired, reconstructed and enlarged. In this period extending for a decade, the architects and the city have got the chance to revitalize these structures from architectural, technical, structural and functional aspect. For the last decade, intensive activities on reconstruction, repair as well as enlargement and building of other storeys on existing old residential buildings has been carried out. Since 1990 we have been witnessing a tendency of avoidance of compliance with legislative regulations and decreasing of proportions of bearing elements as well as uncontrolled behaviour of structures under gravity loads and external seismic effects. The reasons for such an extensive reconstruction and building of other storeys onto old residential structures is the increasing need of residential area, revitalization and repair of structures that are 30 to 50 years old as well as improvement of the quality of living of the occupants of those structures. However, this poses a problem since the existing structures are designed in different time and with different resistance to seismic effects. The interventions that are being done on residential structures most frequently include enlargement of balconies and building onto the last plate to obtain residential area at another or two levels as well as enlargement of structures in both directions. There is also a structural problem that arises when in these structures that are highly vulnerable, openings are made into the bearing walls to enlarge balconies and built other storeys. Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
126
Reconstruction, Enlargement, Adding Storeys and Revitalization
2 PROBLEM CONCERNING STRUCTURE 2.1 Typology of structures For period of 1948-1963 mainly two type of structural systems are build in Skopje for residential buildings - solid brick masonry, with or without reinforced concrete horizontal and vertical belt courses and prefabricated large panel RC systems. 2.1.1
Solid brick masonty structures
Masonry has been one of the main construction materials because of its quality as a thermal insulator, acoustic insulator, its hygroscopicity, etc. However, the experience from occurred earthquakes points to unfavourable behaviour of masonry structures since it is the masonry structures that have suffered mass failure and heavy structural damage during past earthquakes. Masonry structures are massive and have a high bearing capacity of walls under compression, insufficient bearing capacity under tension, low ductility capacity and inadequate connection of the structural elements into a whole, particularly improper interconnection of the bearing walls in both orthogonal directions and inadequate connection of the bearing walls with the floor structures. a) Bearing walls constructed of solid brick without horizontal and vertical RC belt courses The bearing structural system consists of bearing walls constructed of solid brick in lime or cement lime mortar. The bearing walls are in longitudinal, transverse or both orthogonal directions. The disposition of the walls depends on the distribution of the premises, the horizontal and vertical communications. The walls are partially inter-connected by timber beams. The structure is founded on strip foundation constructed of stone in lime mortar. The floor structures are constructed of wood. The roof structures are made of timber with a roof cover most frequently constructed of ceramic tiles. b) Bearing walls constructed of solid bricks with horizontal RC belt courses The bearing structural system consists of bearing walls constructed of solid brick in lime or cement lime mortar, in both orthogonal directions, strengthened and inter-connected by horizontal RC belt courses at the level of the floor and roof structures. The disposition of the walls depends on the distribution of the premises, the direction in which the floor structure is supported, the outlets beyond the outline of the structure, the horizontal and the vertical communications. The structure is founded on concrete strip foundation. The floor structures are precast RC fine ribbed type AVRAMENKO. The roof structures are constructed of timber, with roof cover most frequently constructed of ceramic tiles. c) Bearing walls constructed of solid brick with horizontal and vertical RC belt courses The bearing structural system consists of bearing walls constructed of solid brick in lime or cement lime mortar, in both orthogonal directions, strengthened and inter-connected by horizontal and vertical RC belt courses. The vertical RC belt courses are constructed after construction of the walls. The disposition of the walls depends on the distribution of the premises, the direction in which the floor structure is supported, in one or both directions, the outlets for terraces and bay windows beyond the outline of the structure, the horizontal and vertical communications. The structure is founded on concrete strip foundation. The floor structures represent semi-precast RC systems or monolith RC slabs. The roof structures are constructed of timber, with a roof cover constructed most frequently by use of ceramic tiles.
Reconstruction, Enlargement, Adding Storeys and Revitalization
2.1.2
127
Reinforced concrete structures
In the second half of the twentieth century, there started to be constructed buildings with RC frames and walls in both orthogonal directions. The floor structures of these buildings are constructed as semi-precast reinforced concrete. Since 1963, the structures have been designed to sustain external gravity and seismic effects. The structural systems have sufficient strength and rigidity and a considerable deformability capacity and ability for seismic energy dissipation. It is possible to design the systems to have controlled and dictated resistance to seismic effects. 2.1.3
Prefabricated large panel RC structures
After the Second World War, the increase in population and hence in the demands for residential space especially in Europe, have given rise to an extensive development of prefabricated structural systems as a substitution for the traditional monolithically constructed elements. The main difference between the prefabricated and monolith structures is that the prefabricated structures consist of elements that are cast in place different than the final position of the element in the structure. The elements constituting the structure are produced in factories from hence they are transported to construction site, mounted and connected by horizontal and vertical joints into an integral whole. The structural configuration for resistance against vertical and horizontal loads consists of structural walls, frames formed of beams and columns and systems consisting of interconnected walls and frames. Available is a wide range of prefabricated reinforced concrete structural elements like concrete blocks, beams and columns up to complete rooms or buildings known as "box" units. In the beginning, prefabricated elements were developed in non-seismically active regions and for low-rise structures of up to five storeys. The development of the technology of production and assemblage enabled development of these systems which became applicable also in the seismically active regions in Europe, North America, South America and Japan. Today, prefabricated buildings with a height of ten to twenty stories are frequently found in seismically active regions of many countries all over the world. Applied are three levels of industrialization: structures with prefabricated floor and roof structures and monolith bearing walls, prefabricated floor, roof and wall panels and finishing works performed in a traditional way, and prefabricated floor, roof and wall panels with finishing works (most or all) performed in factory using industrialized methods. The mass construction of large panel systems initiates the need for design of stable and economic systems. Their mass construction in seismically active regions increases the seismic risk, so that errors made in the design and construction might induce heavy consequences during strong earthquakes. The stability of these buildings depends on: the production technology, the way of connecting the structural elements, the composition of the elements, the reinforcement, the configuration of the contact areas of elements and the system of joints. The behaviour of the prefabricated large panel reinforced concrete systems depends on the behaviour of their constituent elements - vertical wall panels, horizontal panel slabs, vertical and horizontal connections. So far, during the design and analysis of large panel systems under static and dynamic loads, the vertical wall panels have been considered to behave in elastic range. They are designed with identical proportions and reinforcement distributed along the height of the building. They are reinforced by a relatively high pecentage of vertical and horizontal reinforcement, often with a non-controlled mechanism of behaviour up to ultimate states of strength and deformability. The vertical and the horizontal joints are considered to behave in the nonlinear range, most of the total energy being dissipated through them. After the occurred earthquakes, cracks and damages in the vertical wall panels have been observed which means that they suffer nonlinear deformations and damages due to the complex
128
Reconstruction, Enlargement, Adding Storeys and Revitalization
stresses induced by moderate and strong earthquakes. Diagonal caracks have not been observed. The same has been proved by the results of experimental investigations of fragments of large panel systems. The large-panel precast system "KARPOS" wich represents modified Soviet system which has been especially designed for the needs in Skopje. The structural system consists of bearing vertical, central and facade reinforced-concrete wall panels supporting the floor panel slabs. The panels are interconnected by vertical and horizontal wet joints filled with cast-in-place concrete. The system is applied in buildings with a height of 4-5 soreys, whereas the theoretical and experimental investigations were done for a building with 9 storeys. 2.2 Problems a) Damages Due to the ravages of time, improper maintenance and design/performance defects in the course of time, both types of structures have suffered different extent of damage and require proper maintenance, i.e., increase of seismic resistance to the level compliant with the legislative regulations. This is particularly true for structures constructed prior to the effectuation of the Rulebook on Construction of High-rises in Seismically Prone Areas. b) Interventions The interventions that are most commonly being done on old residential buildings involve enlargement of balconies that are frequently transformed into built residential areas, enlargement of building outlines along a vertical and horizontal line (Fig.1), building of residential attics, sometimes a story and an attic, renovation and repair of facades, opening and/or enlarge openings in external and internal walls and sometimes change of weathered installations and construction of elevators. There is also a structural problem that arises when in these structures that are highly vulnerable, openings are made into the bearing walls to enlarge balconies and built other storeys. Figure 1. Relationship strength – deformability, existing and upgraded structure
Reconstruction, Enlargement, Adding Storeys and Revitalization
129
2.3 Actions a) Loads Vertical – Gravity and Live Loads Horizontal – Wind Load Exceptional Loads Earthquakes Explosions b) Actions Age of structures Intervention on structures Changing ground floor to public space, shops, etc Rebuilding inside Adding on the side of buildings (balconies, galleries, rooms) Tower: to give stability (connected to the existing construction Adding on top “just” adding Maintenance 2.4 Solutions 2.4.1
Strategy for improvement Rebuilding Repair of damaged structures Repair and strengthening of damaged structures Repairing and strengthening of existing no damaged structures Repair, strengthening, adaptation, reconstruction and revitalization of the existing structures Strengthening of the existing structures Revitalization of the existing structures
2.4.2
Description of works
a) Repair and Strengthening Design of repair and/or strengthening is done by complying to the requirements of the valid technical regulations and the most recent knowledge in aseismic design and behaviour of this type of structures by controlling of strength, rigidity, deformability and ability for seismic energy dissipation of bearing elements and the system as a whole. Repair and strengthening of existing damaged or non-damaged masonry structures is performed by controlled and dictated increase in strength, rigidity, deformability and ability for dissipation of seismic energy of the bearing elements and their connection into an integrity capable of accepting and transferring gravity and external seismic effects. The usual mode of repair of damaged walls is injection, strengthening by use of RC jackets, replacement of timber floor structures by flat RC slabs as well as their interconnection in both orthogonal directions. This gives rise to a quite extensive modification of the characteristics of the structure for the purpose of sustaining external and static and dynamic loads (Fig.2).
130
Reconstruction, Enlargement, Adding Storeys and Revitalization
Figure 2. Force - displacement diagram for masonry and R/C elements
Representative bilinear storey diagram
Cumulative storey diagram - RC elements
K=4160 [kN] LP=0.11 Gy=1.13 [cm] Gu=4.20 [cm] Qy=4700 [kN] Qu=6100 [kN] D=3.72
Cumulative storey diagram M ll l t Individual RC elements Individual masonry wall elements
It should be mentioned that today, there are available numerous computer programmes for analysis, complete knowledge of behaviour of structures under earthquakes, numerous analytical and experimental results and modern materials so that ideal conditions for raising the degree of stability of existing structures have been created. Unfortunately, there is only a small number of design engineers that are able to perform complex analysis of behaviour of existing structures, propose measures for strengthening and perform analysis of stability of repaired and strengthened structure. Recent structures constructed by use of reinforced concrete are characterized by a different degree of safety against expected seismic effects, depending on the level of knowledge of the design engineer. The earthquakes that have occurred and have inflicted heavy structural damage and loss of human lives point out that a step forward should be taken in analysis. This step is consideration of the dynamic response of the structure to actual seismic effects expected at the considered site.
b) Urgent activities for raising the stability level To avoid uncontrolled damage and loss of material goods and human lives in the event of a possible earthquake, an urgent coordinated activity of the technical and administrative potential of the country is necessary to introduce stability of the existing residential fund that will be at an acceptable and legislatively defined level through repair, strengthening and revitalization according to the extent of damages and the level of resistance of the structures under gravity and seismic effects. In the case of enlargements and building of other storeys, there is a need of a complex analysis of strength, rigidity and deformability of the existing and the new structural system for the purpose of designing and constructing an integral system with controlled and dictated ductile behaviour during occurrence of strong earthquakes. This is particularly expressed in the process of building of other storeyes on structures where the design engineer is forced to design enlargement of a relatively narrow and high structure as is the case with enlargement of balconies. The newly designed and the existing structure are often with completely different characteristics and behaviour under dynamic loads. In that case, during design, it is endeavoured that the structure composed of an existing and a new part has a
Reconstruction, Enlargement, Adding Storeys and Revitalization
131
controlled behaviour under gravity and seismic effects whereat both parts shall together sustain the external effects. In conclusion, dynamic response of the enlarged structure to seismic effects on the considered site (with their intensity and frequency content) should be controlled. 3 CONCLUSIONS The inherited concept of the urban area and the old damaged buildings are part of the architectural reality that surrounds us and these structures and urban units that need reconstruction, repair and revitalization should be treated by a well conceived professional and mature approach in order that we might achieve spatial and architectural continuity of amending and developing the city architecture. Such a well conceived professional and mature approach to intervention on existing urban units should be developed at several levels. The analyses of old residential structures and complexes suffering different interventions can be made from a number of aspects, i.e., structural, functional, architectural and urban, whereat there are certain advantages and disadvantages arising from the way in which the problems of the buildings are solved. To satisfy the requirements of seismic design of high-rises in seismically active regions, it is necessary to apply a modern design concept that apart from the strength and deformability shall take into account the plastic excursions and the capability for seismic energy dissipation. Namely, it is necessary that elements that shall eliminate the unfavourable behaviour of masonry and enable its favourable behaviour be incorporated in masonry structures during their design or repair and strengthening. Most frequently, a solution is found in combining masonry with other materials that are characterized by a high ductility, tensile and shear strength. From structural aspects, analysis of the stability of existing types of structures should be made and an efficient and economic way of their strengthening and revitalization by satisfying the requirements of the valid technical regulations, based on the most recent knowledge on seismic design and behaviour of this type of structures, exposed to external gravity and seismic loads, controlling the strength, stiffness, deformability and capability of seismic energy dissipation of the bearing elements and the system as a whole. While revitalizing the structures, modern technical solutions in respect to improvement of the infrastructure of the structure and their modernization from functional, technical and spatial aspects should be applied. There should be established certain concepts for enlargement, building of other storeys, repair and revitalization of structures and urban units to achieve continuity and improvement of their architecture and the urban area in which they are in order to achieve a new quality of the city regarding ambient, aesthetic and functional dimension. 4 REFERENCES Bozinovski, Lj., Z., “Improving The Quality Of Existing Urban Building Envelopes”, EE-21C, International Conference on Earthquake Engineering, 27 August-1st September 2005, Skopje-Ohrid. Pavlovska, R., and Bozinovski, Lj., Z., “Reconstruction, Repairing, Enlargement and Building of another Storey of Existing Buildings Apartments in Skopje”, Proceeding of the First Congress of the Engineer’s Institution of Macedonia, Srtuga, Macedonia, Oktomber 24-26, 2002. Bozinovski, Z., Stojanovski, B., and Petrusevska, R., "Repair and Strengthening of the Main Structural System by Analysis of the Stability of the Primary School Buildings in the Commune of Bitola”, IZIIS Report 95-26 to 95-45, 1995.
This page intentionally left blank
Adding Two Storeys to Existing Building A. Kozáowski, Z. Plewako & A. Rybka Rzeszów University of Technology, Poland
ABSTRACT: One of the possible solution for enlarging useable space for existing building is to add stories. Adding new stories involves additional loadings to old structure and to subsoil. Very often calculation and analysis of existing structure and overloading of soil leads to conclusion, that only very lightweight superstructure can be applied. One of such structure can be prefabricated steel frame-panel SUNDAY systemTM which includes pre-engineered wall panels, roof trusses, headers and joists in fabrication shop from light-gauge steel stud made on the rollform machine. The combination of only 2 shapes (C and U) in 2 sizes each, with addition of 4 kinds of screws and using different steel gauges for these shapes is able to totally fulfill structural requirements of any structure type specified by the designer for such use. The paper present the case study of application of light steel prefabrication technology for enlargement of existing building by two additional stories. 1 GENERAL DESCRIPTION OF THE CASE STUDY This paper presents one of possible solution for enlarging useable space for existing building. Though presented building is not a housing object, described technology can be also applied for dwelling houses. Permanent demand of dwellings typical for Poland and lack of efficient economical possibilities for building new flats forced such a cheap and fast solution. Considered building is located in campus of Rzeszów University of Technology (Fig. 1). It was originally erected in the turn of 50s of XX century for Building Craft School in Rzeszów, and in 1967 took over by Civil Engineering Faculty of Rzeszów Technical High School. It was used as a didactic building for students with office rooms for staff. It was a three storey building, with underground level under part of structure. It’s length is 64,17 m and width differs from 18,70 m on east side, 12,40 m in mid-part and 22,04 m on west side (Fig. 2). Height of the underground is 2,6 m, of the 1st and 2nd floor 3,5 m and for 3rd varies according to roof slope from 3,2 by the elevations to 3,6 in the centre. Total height of building was 11.4 m. Ground area was 918.40 m2, usable area 2 384.41 m2, and usable space 10 715.70 m3. Some rooms in ground floor are functionally separated and connected with sport hall located on the south side of the building.
Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
134
Adding Two Storeys to Existing Building
Figure 1. View of existing building before reconstruction.
64,17
22,04
18,70
Figure 2. Dimensions of the building.
Needs for additional space resulting from enhanced number of students and development of research activity gave the background for modernisation actions performed for this building in three stages: 1o new research laboratory for structures and soils with facility areas (1998), 2o new lecture block (2002), 3o heightening of main (old) structure with 2 levels for lecture and office area (2004). First two stages result in execution of two new parts, functionally connected with old building but structurally independent. Considering 3o stage, adding two extra stories over old structure gave 1704,90 m2 of usable area (70% enlarging of existing area in old building). This project was carried out in three holiday months of 2004 year.
Adding Two Storeys to Existing Building
135
2 PROBLEM CONCERNING STRUCTURE 2.1 Typology of structure The building was erected in traditional technology (Fig. 3). Concrete foundation strips located 1.5 m under ground level were applied (Engineering and architectural inventory 1994). The foundation walls and structural walls (45 cm wide) as well as partitions (14 cm) were made of brickwork . Stairs made of reinforced concrete. Reinforced concrete one-span ceilings with ceramic filling were used. The main span length is 5.65 m, for corridors 2.15 m . Flat (5% slope) roof on 3rd floor ceiling with slag insulation layer covered with bituminous paper on concrete base was applied (Fig. 4).
Figure 3. Ground floor plan of old building (Engineering and architectural inventory 1994 )
Figure 4. Longitudinal cross-section of old building.
2.2 Problems Considering existing condition of the building according to planned action three problems occurred (Expert opinion 1994): - adding new stories involves additional loadings to old structure and to subsoil. Calculation and analysis of both: structure and relatively week soil showed, that only very lightweight two storey superstructure can be applied, - the U-value for old envelope was much below limits resulting for actual energy saving requirements. So, the decision was to replace old windows to smaller new with appropriate thermal resistance. Another conclusion was to apply ETICS (External Thermal Insulating Composite System) layer to existing façade, - the only possible period for construction works was three months during summer holidays, because during semesters the lectures must go on. So, new structure must be easy and fast to assembly, with minimum intervention into old one.
136
Adding Two Storeys to Existing Building
2.3 Actions Considering all mentioned limits, the decision was to apply for new structure prefabricated steel frame-panel SUNDAY systemTM delivered by AmTech firm (Design of overbuild for “P” building 2003). Only reinforce concrete stairs in brick wall staircases was applied. SUNDAYsystem¥ (AmTech 2005) includes pre-engineered wall panels (Fig. 5), roof trusses, headers and joists in fabrication shop from light-gauge steel stud made on the rollform machine. The combination of only 2 shapes (C and U) in 2 sizes each, with addition of 4 kinds of screws and using different steel gauges for these shapes is able to totally fulfill structural requirements of any structure type specified by the designer.
Figure 5. Light gauge steel wall panels during erection
The bearing structure scheme generally repeats the old one, where one span ceiling were supported on external walls and internal longitudinal ones. All panels were preliminary prefabricated, base on the geometry of existing structure. The panels consist of cold-formed C- or U-shapes 90 mm and 140mm high, made of steel sheets 0.9 mm, 1.25 mm, 1.50 mm, zinc coated. Profiles in panels are fastened by self-drilling bolts (AmTech 2005). Necessary preliminary works dealing with ventilation system, electric and network wiring was performed in evenings and nights or in week-ends. The decision was to install for all building new ventilation shafts with steel channels and new wiring before construction works, with existing systems still working. The heating system have been replaced and prepared for new parts during the main construction works. Also rearrangement of some partitions and other changes in old part were done in the same time. Old windows were replaced before the action, and the ETICS were installed after finishing all works on new stories elevations.
Adding Two Storeys to Existing Building
137
2.4 Description of works
Figure 6. SUNDAY steel frame superstructure under assembling.
3rd stage of modernization actions performed for this building started in spring of 2004 with installing of new gravity ventilation shafts in existing rooms (Design of overbuild for “P” building 2003). After punching appropriate holes in ceilings, steel channels were installed and masked behind gypsum-board panels. The attics walls and chimneys on roof were cut to required level. New base walls around roof over external walls were done for superstructure panels. Slope of old roof structure was leveled by floor structure made of SANDAY panels. All panels used for walls, floors and new roof were stiffened by Oriented Strand Boards (OSB) as a base for finishing and elevation layers.
138
Adding Two Storeys to Existing Building
Figure 7. Cross-section of additional stories with suspended ceilings (Design of overbuild for “P” building 2003)
Accordingly, existing stair cases were erected, stiffening all structure. External walls are made of steel posts (the C 90 or C 140 C-shaped profiles), their spacing equal to 60 cm, placed in the U 90 or U 140 U-shaped profiles, which constitute the basis and the closure of a wall. Transverse bracing and spandrel beams are made of steel strips or appropriately cut profiles. Wall panels, assembled in the factory, provide for window and doorway openings, and include lintels of a special design. Finishing of internal surfaces of steel wall panels was made of gypsum board. For external walls, on impregnated OSB board with PE vapour membrane, 8 cm of mineral wool was placed, and covered by “Reynobond” aluminum composite panels with polyethylene filling. Additional layer of thermal insulation of the thickness equal to the height of steel profile were applied inside panel walls. For inter-story floors, the C 90 and C 140 C-shaped profiles, as well as the U 90 and U 140 U-shaped profiles are used, in different configurations. The typical spacing of the beams is 60 cm. Floor finishing was made from PVC lining on the base of gypsum-fiber board ”Fermacell” separated by 1 cm of mineral wool layer of OSB board. Suspended ceilings of gypsum board with alu frame were used. The load bearing structure of the roofs is constituted of steel trusses made of the C 90 and C 140 C-shaped profiles. Truss joints are covered with metal sheets on both sides. Connections are executed with the use of sheet-metal screws. The constituent elements of the girders are joined directly. Bracing of the roof structure is executed with the use of the C 140 or C 90 C-shaped profiles. The typical roof girder spacing equals 60 cm. Warm roof consist of AmTech structure with OSB boards, then PE vapour membrane and 20 cm of mineral wool as thermal insulation. External waterproof layer made of “Rhenofol CV” roof membrane on 1 cm of “Braas” glass fibre fabrics.
Adding Two Storeys to Existing Building
139
Figure 8. Building under construction works.
Figure 9. Old building in “new suit”.
3 CONCLUDING REMARKS Presented case study is typical for cases when increased loading from additional stories excludes application of traditional brickwork technology. One of possible solution to use is light gauge steel prefabricated technology. Application of such technology was described in details in the paper.
140
Adding Two Storeys to Existing Building
REFERENCES: Engineering and architectural inventory of “P” building and Small Sport Hall in Rzeszów University of Technology, Rzeszów UT, March 1994. Expert opinion on technical condition and possibility of adding new stories for “P” building in Rzeszów University of Technology, Rzeszów UT, April 1994. Design of overbuild for “P” building in Rzeszów University of Technology, Architectural Study “SáapiĔski”, Rzeszów, June 2003. SUNDAY systemTM light gauge steel technology. AmTech, Rzeszów, 2005.
Annex of Attics on Flat Roofs of Urban Residential Buildings Aleksandra Krstic-Furundzic Faculty of Architecture, University of Belgrade, Serbia
ABSTRACT: Necessity for rehabilitation of flat roofs, as well as residential deficit and high prices of flats caused massive annex of attics. In Belgrade in the period after World War II mass building of apartment houses with flat roofs had been extensively used. Flat roofs appeared functionally unsuitable in domestic climatic conditions. Because of improper technical solutions and building practice, flat roofs leaked, causing bad living conditions in flats underneath. As a sloped roof in our environment is traditional form functionally favorable for our climatic conditions, the solution was in annex of attics, representing a characteristic example how climatic conditions create the renewal of existing buildings and urban spaces. The most important benefits to the community are improvement of technical and living conditions in the whole building, especially on the original top floors, and efficient and cost-effective building of new dwellings, as well as improvement of buildings and settlement appearance. Through review of several examples realized in Belgrade, survey of some technique solutions for annex of attics will be given in the paper. Improvement of building appearance will be also discussed. 1 INTRODUCTION In Belgrade in the period after World War II mass building of apartment houses with flat roofs has been extensively used. Because of improper technical solutions and building practice, flat roofs leaked, creating poor living conditions in flats under roof. Sloped roof is a traditional form functionally favorable for our climatic conditions. Necessity for reconstruction of flat roofs and housing shortage, increased by great number of last civil war refugees from former Yugoslavia parts, as well as the insufficiency of housing space in existing flats and high prices for newly constructed buildings, caused massive annex of attics on top of flat roofs especially in suburban areas. These attics were usually built for the purpose of dwelling. Strategy is to increase the number of flats without increasing the number of buildings on the same site and to use the existing infrastructure, thus reducing the cost per sq. m. built in the attic that varies from 700 to 1200Euro/m2, depending on location and structure type, while price of newly constructed flats ranges from 1000 to 2000Eura/m2 (luxury apartments are not taken into consideration). 1.1 Situation before annex of attics For most cases, situation before annex of attics was similar and can be described as follows: - mass postwar construction of housing structures with flat roofs, - suburban new housing settlements looked monotonous and did not fit into the environment building spirit, - the ratio of the number of inhabitants and free areas in the settlements allowed an increase in the housing stock, - the flat roof proved to be functionally unsuitable in domestic climatic conditions, Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
142
Annex of Attics on Flat Roofs of Urban Residential Buildings
- inadequate technical solutions and building practice, as well as the poor quality of material, resulted in frequent leaking of the roofs, creating poor living conditions in flats underneath, - repair needs, as well as the insufficiency of housing space and high prices for newly constructed buildings, led to the phenomenon of mass building of attics on top of flat roofs, especially in suburban areas, as a sort of bioclimatic rehabilitation. 2 STRATEGY Strategy of attics annex on flat roofs can be treated in three directions: idea, auxiliary activities and benefits for the community. 2.1 Idea By building attics on a top of flat roofs, it is possible to obtain: - an increased number of housing units without increasing the number of buildings on the same site, - the expansion of housing units on top floors of the existing buildings, - the use of the existing infrastructure, thus reducing the costs per sq. m. built in the attic, - a repair of flat roofs and improved living conditions on the original top floors, but improved technical conditions of the entire building, - better incorporation into the spirit of the environment and the existing structures, - visual identity of the existing buildings and suburban housing settlements from the Moderna period. 2.2 Auxiliary activities The building of attics on top of flat roofs leads to new programs and tasks for the builders, legislators and industry: - the lack of previous experience in the construction of dwellings in attics requires scientific research of spatial and organizational performances of attics [3], the factors of comfortable living [2, 5] and principles for implementation in order to ensure good living conditions, - the need to elaborate standards and recommendations for the design and construction of new attics, as well as for adaptation of existing ones, - a development of (industrial) systems for building attics on top of flat roofs, which would enable rapid and cheap construction without disturbing the life of the tenants, - elaboration of new, and the adjustment of the existing production programs of the building industry, for manufacturing additional equipment for attic dwellings. 2.3. Benefits for the Community The most important benefits for the community, that give support to annex of attics, are the following: - improvement of technical and living conditions in the whole building, specially on the original top floors, - efficient and cost-effective building of new dwellings, within the framework of the existing housing stock and infrastructure, - attainment of visual identity of buildings and settlements, with a positive effect upon the psycho-sociological condition of the users.
Annex of Attics on Flat Roofs of Urban Residential Buildings
143
3 ATTICS ANNEX BUILDING TECHNIQUES Annex of attics on flat roofs of apartment houses impose specific demands. Weight of annexed construction is limited in order to minimize additional load of existing construction, which is statically determinate, unchangeable or rare adaptable, and in most cases made of concrete monolithic or prefabricated construction. In that sense, light roof constructions, wooden and metal, are the best applicable for attics annex. Preventing their raise under wind load, they must be properly anchored to existing construction. Annex of attic must not disturb tenants on standard floors and has to be carried out in the most effective way. Priority is given to industrialized construction methods, as quicker and with less work on site. In general attic and existing standard floors construction can be in following relations (Krstic, 1995): 1. Attic construction does not come from building system. They are often made of different material. Mutually they usually represent construction entirety (Fig. 1), 2. Attic construction comes from building system, including the following options: a) both made of the same material (Fig. 2a), b) main roof load-bearing members are made of the same material as building - mixed construction (Fig. 2b, b'), c) whole attic construction made of different material, but represents logical extension of building system (Fig. 2c).
Figure 1. Attic construction does not come from building system.
Figure 2. Attic construction comes from building system: a/ the same material and constructive system, b/ mixed construction, c/ construction continuity - different materials.
144
Annex of Attics on Flat Roofs of Urban Residential Buildings
Described relations between an attic and a standard floor construction can be treated as methods for building of attics on the top of flat roofs. The most usable methods are variants 1, 2b,b' and 2c. Variants 1 and 2b' enable application of prefab members and in factory assembled roof space unities with thermal and humidity insulation built in. Variant 2a is convenient for new houses building. According to space usability in dependence on construction type, attics can be: useless (construction disable use of space), partially usable and completely usable. There are two conceptual options for attic enclosure materialization (Krstic, 1996): as roof (Fig. 3-II) and as combination of facade and roof surfaces (Fig. 3-I). It strongly influences buildings and settlement appearance. The first option is more favorable because it does not extend and change existing facade, but makes impression that a house has a roof. In many cases results are better functional performances and building appearance. But in the other hand the consequence is a loss of main Moderna period characteristic what flat roof was. Unusable zones (by the eaves, in the roof top) and garret behave as "tampon" zones (Fig. 3-III), that contribute to reduction of heat losses.
Figure 3. Conceptual options for attic enclosure materialization: I. as combination of facade and roof surfaces and II. as roof surfaces. III. Unusable areas as "tampon" zones.
Design of superstructure can have following approaches: - opposite to existing building appearance, - harmonized to existing building appearance, - hidden if roof terrace is created behind roof parapet. Different requirements and limitations are present in cases of attic annex in the central city zones and in suburban areas. Particularly delicate are actions in the city centre. Knowledge of roof and eave types background is important. Annex of attic is allowed if the house is not built up to height permitted in appropriate urban plan, providing better facade regulation, and if it does not endanger house stability and living conditions. Attic annex can cause reinforcement of old house’s structures according to the current seismic and technical regulations. In central city areas annexed forms usually fit into surroundings imitating existing roofs and eaves forms. In practice are roofs with parapet, mansard roofs and "false" mansards, indicating different usability of zone by eaves. In case of roofs with parapet, parapet height reflects in facade enlargements. The same construction and material types of existing facade are usually used for parapet construction. Indentation of attic can be supplied if roof terrace is created, providing annex of attic to be hidden. More then one story can be formed without influencing existing facade. In suburban housing settlements annex of attics is carried out as organized action and giving priority to industrialized building methods. Due to absence or incomplete of development plans of urban areas, annex of attics was usually carried out without building permit. Mostly such actions later got permits. It resulted in chaotic situation and esthetic demotion of town silhouette. Development of methodology for planning and design of annex of attics is a key for solution of listed problems and organized
Annex of Attics on Flat Roofs of Urban Residential Buildings
145
actions. It must take into consideration analyzes of traditional roof forms, forms suitable for dwelling purposes, comfort factors of dwelling in attics, construction and design principles and ratio of tenants number and green areas, parking places, open public spaces, because annex of attics increases number of tenants. Public utilities and infrastructure must carry out additional load. Annex of attics has to be profitable in building as well as in usage stages. The purpose, flexibility and maintenance have to be considered. Tenant participation in the processes of decision-making, regarding necessity, purpose and design of attics, is of great interest for creation of positive effect upon the psycho-sociological condition of users, particularly in current conditions of private property. Attics housing space has the same comfort criterions as standard floors, even more strict. Attics of multistory buildings, because of their specific position, are strongly exposed to atmospheric influence. Ratio of living area (attics volume) and the area of outside walls is more negative for attics than for standard floors, that way energetic losses in winter and overheat in summer are bigger. Ventilated structures of light and massive roof constructions are proved as solutions that obtain thermal comfort in attics made in purpose of dwelling. For Belgrade climatic conditions massive roof construction, because it provides heat accumulation, is favorable. Light roof constructions are the best applicable for attics annex, requiring min. 12-15 cm. thermal insulation thickness (mineral wool or polystyrene, providing U value lower then regulated 0,65W/m2K) and ventilated roof structure, which prevents overheat, leads vapor out and prevents condensation (Brennecke, Folkerts, Haferland, Hart, 1984). The most suitable roof cladding is corrugated metal roofing because it is light and easy for covering. Greenhouses can be incorporated very successfully in roof design (by aspect of form, economy and construction) and used for solar heat gain. Very often it happens that later on, tenants by themselves glaze balconies and loggias. Greenhouse oriented to several rooms is favorable. Attic flats have better exposure to solar radiation than standard floors. Supply of solar heat gain can influence choice of roof form and slope. Roof windows can provide sun heat to flat areas that are distant from south facades. 4 ATTICS ANNEX EXAMPLES There are many examples of building on top of flat roofs realized in the center zones and in peripheral settlements of Belgrade. Examples built in peripheral settlements are characterized by mass annex of attics that caused standard design of attic flats, though making its variations possible, and creation of attic annex construction systems. In all cases existing tenants did not leave their flats. To protect the last floor dwellers from eventual soakage during works on superstructure, the assembly phases are though out in such manner to perform the covering of the entire roof terrace first, and then to perform the assembly of the remaining construction contents under the formed "tent". Elements of a superstructure are classified according to the following: elements of construction, elements of internal and external walls, of ceiling, floor and roof cover, windows and doors and brought on the objects in a succession of envisaged assembly phases. The building materials were often erected from gable sides of houses. Because of better thermal and acoustic insulation and fire protection solid parapets and external walls were built in many cases. The roof floor is usually made as light construction. The closing and covering of the attics were carried out by using domestic technologies, products and material. Peripheral settlements Uciteljsko naselje (Fig. 5), Konjarnik (Fig. 6, 7), Block of flats No 23 (Fig. 8, 9) and Miljakovac (Fig. 10) can be separated as interesting examples of massive annex of attics. At Uciteljsko naselje attic construction does not come from a building system. It is made of prefab wooden trussed girders which form frames or arches. Special wooden construction, that forms openings, is supported by them.
146
Annex of Attics on Flat Roofs of Urban Residential Buildings
Figure 5. Attics annex at Uciteljsko naselje - attic construction made of wooden trussed girders
Attics at Konjarnik and Block 23 have the similar construction concept. In the first case is mixed construction like on Figure 2b', with prefab wooden trusses (Fig. 6), and in the second is light construction, like on Figure 2c, with prefab steel trusses used to form "false" mansard roof (Fig. 8, 9). Location of rainwater gutter is on the upper position, as on the Figure 3.I.b.
Figure 6. Attics annex at Konjarnik - attic construction made of prefab wooden trusses
Annex of Attics on Flat Roofs of Urban Residential Buildings
a) Before attic annex
147
b) After attic annex
Figure 7. Attics annex at Konjarnik
In the case of the steel attic carrying structure, static spans and construction grid are conditioned by objects’ structure and they are correspondent to the arrangement of construction supports in lower floors. The new construction is a skeleton construction and it is bound to the object just on the spots of support of vertical columns which are in the existing reinforced concrete structure. All walls and ceilings are self-supporting, and they are designed as assemblies of prefabricated members (Fig. 8, 9).
Figure 8. Attic construction made of prefab steel trusses
148
a) Before attic annex
Annex of Attics on Flat Roofs of Urban Residential Buildings
b) After attic annex
Figure 9. Attics annex at Blok 23 - attic construction made of prefab steel trusses
At Miljakovac the structural system of the attic is a mixed construction as shown on Figure 2b. Reinforced concrete structure of galleries and wooden roof skeleton are supported by masonry walls being a continuation of existing structural walls (Fig. 10). At Miljakovac, after the construction of attics, the building and settlements obtained the following properties: the attics were built on top of 59 structures with flat roofs, in each of the attics, on every building, 6 dwellings were built; rationalization of land use - the number of apartments was increased by 1/6 of the original; on the original top floors the overheat and extreme heat losses were stopped, good living conditions in the attics were ensured by using the ventilating system in the roof ceiling.
Annex of Attics on Flat Roofs of Urban Residential Buildings
Figure 10. Attics annex at Miljakovac settlement - mixed construction
149
150
Annex of Attics on Flat Roofs of Urban Residential Buildings
5 CONCLUSION Realized building on top of flat roofs and the situation after, point out that annex of attic is a useful measure in renewal of existing buildings and urban spaces in our environment. In an intention to provide the best practices and results, annex of attics demands activities as: - definition of strategy - idea, auxiliary activities and benefits for the community, - scientific research of spatial and organizational performance of attics and principles of attic materialization, all in aim to make appropriate living conditions, - a development of (industrial) systems for annex of attics on top of flat roofs, which would enable rapid and cheap construction without disturbing the life of the tenants and provide aesthetically and functionally successful designs. REFERENCES Brennecke W, Folkerts H., Haferland F., Hart F. 1984. Dachatlas - geneigte dacher: 104-117. Munchen: Institut fur internationale Architektur - Dokumentation GmbH. Krstic A. 1995. Kos krov u domacoj stambenoj arhitekturi-tradicionalan i savremen Arhitektonski element (Sloped roof in domestic residential architecture - traditional and modern architectural element), Edition ARHITEKTONIKA, series A - volume 8: 46-49. Belgrade: Faculty of Architecture. Krstic A. 1996. Faktori komfora stanovanja u potkrovlju (Comfort factors of dwelling in attics). In Milemkovic M, Ralevic, M, Kurtovic-Folic, N (eds), Stanovanje iz sadasnjosti ka buducnosti (Dwelling from present to future), Edition ARHITEKTONIKA, Volume 9: 307-332. Belgrade: Faculty of Architecture.
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands M.T.Andeweg Department of Real Estate and Housing, Delft University of Technology, the Netherlands
F.W.A.Koopman Department of Architecture, Delft University of Technology, the Netherlands
ABSTRACT: The renovation of the housing project from 1967 on the Siersteenlaan in Groningen demonstrates that in an integrated approach a wide range of objectives to improve existing buildings can be reached. In this project the goals were the improvement of the urban situation, the architectural appearance, the social control, diversification of dwelling types and a higher functional quality. The solution of the problems was specifically adapted to the existing ‘Rottinghuis’ building system. Large one- and two-floor apartments were created on the ground floor, and the accessibility of the remaining smaller apartments on the upper floors was improved by adding elevators. With diverse additions to the existing buildings different problems were solved. By making as little changes to the structure as possible, the intention to develop more diversification was reached at acceptable cost. 1 GENERAL DISCRIPTION OF THE CASE STUDY This project, dating from the late sixties is located on the Siersteenlaan in the neighbourhood Vinkhuizen of the city of Groningen. It was originally designed by architect F. Klein as social housing for families. The design for the renovation is by ‘Karelse en van der Meer Architects’ in Groningen (nowadays called ‘DeZwarteHond’). In the year 2003 they were awarded for this project the National Renovation Price, a prestigious architectural price that is awarded in the Netherlands every other year since 1987. This renovation project was commissioned by the local housing association Nijestee. The project consisted of three identical multi-family building blocks, dating from 1967, and originally containing a total of 108 uniform three bedroom apartments. The building blocks are four storeys high, and before renovation they were approximately 90 m long. Originally the ground floors were designed as store-rooms, and only the upper floors were in use as living quarters. The renovation of the building blocks on the Siersteenlaan was part of a larger scheme aiming to restructure the entire neighbourhood of Vinkhuizen. Viewed on an urban scale, the Siersteenlaan is one of the major roads for through traffic, and originally these large apartment blocks were designed to border the neighbourhood with single family dwellings behind it, and to shield those from through traffic. See figure 1 for the original urban plan. The objectives of this renovation project were manifold. The first priority was to improve the attainability of the shopping centre located opposite the Siersteenlaan for the tenants of the single family dwellings, and secondly to increase social control in the street behind the apartment blocks in order to oppose rampant vandalism, drugs dealing and pity crime. Other objectives were to improve the architectural appearance of the building blocks and to obtain more diversification in the existing housing stock by adding dwellings with a higher functional quality, and suitable for various types of households. All objectives were determined in dialogue with the tenants. The realization of the project was started in 1998 and took four years to complete. Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
152
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands
Figure 1. Original urban plan of the renovation project on the Siersteenlaan in Vinkhuizen, Groningen.
2 PROBLEMS CONCERNING THE STRUCTURE The apartment blocks on the Siersteenlaan were erected in the building system ‘Rottinghuis’. This is a large panel system developed by a Mr. Rottinghuis shortly after World War II., which makes it one of the oldest Dutch post-war building systems. Between 1948 and 1968 in total some 9000 dwellings were built with this system, practically all three and four storey high multi-family housing. The main plant was located in Groningen and because of the high cost of transport the majority of buildings erected in this system is to be found within a radius of 60 km of this plant. In the Rottinghuis building system all window- and doorframes as well as the electrical conduits were incorporated in the walls and façades. See figure 2.
Figure 2. Prefabrication of a façade element in the Rottinghuis building system, windowframes and electrical conduits are incorporated.
The incorporation of the wooden window- and doorframes in the concrete elements caused putrefaction in a short period of time, which necessitated early replacement. 2.1 Typology of structure In the system Rottinghuis all wall, floor and façades elements were prefabricated. According to Dutch building regulations at that time, façades are never load bearing. The load bearing wall elements are ceiling-high, and vary in thickness from 9 to 20 cm with a length up to 3.5 m and a weight up to 3000 kg.
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands
153
The connection between the floor elements and the transversal walls is established with insitu concrete. The tapered ends of the floors are resting on the walls and connected with steel reinforcement. See figure 3.
Figure 3. Vertical intersection of the connection of wall elements with floor elements in the Rottinghuis building system.
The floor system used in the Rottinghuis building system varies over the years. Originally, prefabricated concrete floor elements were used with ledges on the upper side on a 0.40 m interval. In order to reduce impact-sound, the cavities between the ledges could be filled with sand, and on top of these concrete elements a boarded floor was placed.
Figure 4. Vertical intersection of a prefabricated floor element in the Rottinghuis building system.
In later years prefabricated concrete slab floors, finished off with sand-cement were in use. See figure 4. This solution is used in the concerned buildings on the Siersteenlaan in Groningen. Both floor systems were incorporated in the structure with poured concrete. The same concrete slab floor elements were also used for the construction of the flat roofs. These were finished off with two layers of asphalt paper and 3 cm of gravel.
154
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands
2.2 Problems The fact that the apartment blocks on the Siersteenlaan were realised in the Rottinghuis building system, complicated the renovation project in several respects. First of all, as mentioned above, in this building system the prefabricated floor and wall elements are connected with poured concrete, making the removal of walls and floors a labour-intensive and therefore expensive action. The fact that in the Rottinghuis building system all the transversal walls are part of the bearing structure makes it even more complicated to carry out any alterations in the floor plans. A more general problem that applies to Dutch early post-war apartment blocks is the limited height of the store-rooms on the ground floor. In order to increase social control, these storerooms are often to be converted into living quarters. In this project, the ceilings on the ground floors had a height of only 2.42 meter, which means 0.18 meter short of the minimum height as required for living quarters by the present Dutch Building Code. 2.3 Strategy for improvements One of the main objectives -to improve the attainability of the shopping centre- was accomplished by chopping up the three large building blocks into six smaller ones, and creating passages between the dead-end streets perpendicular on the building blocks with the Siersteenlaan. See figure 5 and 6. This ‘chopping up’ of the building blocks created more advantages than just a better attainability of the shopping centre. After renovation, there is no more pity crime in the street behind the building blocks, since this street has also been chopped up into three small parts, all completely overlooked by the new living quarters on the ground floors. The traffic of cars, bikes and pedestrians up and down the new passages increases the social control even further.
Figure 5. One of the new passages between the Siersteenlaan and a former dead-end street.
On a lower scale, social control was improved by the fact that after renovation the average number of households per building block has decreased from 36 to an average of 17,5. The next objective -more diversification in dwelling types and a higher average functional quality- was obtained by creating large one- and two-floor apartments on the ground floor and by adding elevators for the remaining smaller apartments on the upper floors. In order to reduce the cost, the intention has been to develop more diversification by making as little changes to the structure as possible. Since the original floor plans were quite adequate with a living room of 26 m2, a kitchen of 8.5 m2, and three bedrooms of 13 m2, 9.5 m2 and 6 m2, the floor plans of the apartments on the upper floors could remain nearly unchanged. On request however, new kitchens and bathrooms were fitted, in exchange for a rent increase.
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands
155
2.4 Actions In the original design, the three building blocks on the Siersteenlaan were 12 apartments wide. Now, each block was split into two parts by cutting out the 7th and 8th apartment over the full height of the buildings. See figure 6 for the changes on an urban scale.
Figure 6. New urban plan of the renovation project on the Siersteenlaan in Vinkhuizen, Groningen.
As a result of this action, three blocks of six apartments wide and three blocks of four apartments wide were created at the cost of demolishing a total of 18 apartments. In addition, six elevators were added, one for each new building block, to ensure that all apartments on the higher floors would be accessible for senior citizens. On the lower floors two different types of dwellings were realized. In the three larger building blocks, a total of fifteen new single floor patio-apartments have been created by adding new living rooms behind the building blocks, separated from the original block by a private patio. The 6th and last ground floor space of each new building block has been divided into new storerooms for the apartments on the upper floors. The living rooms of these patio-apartments correspond with the singles family houses opposite the street. In each of the three smaller blocks, facing the side-façades of the single family houses, three apartments on the 2nd floor were joined with the store-rooms on the ground floor in order to create a total of nine two-floor apartments with private gardens. Again, the last ground floor space of each building block is in use as store -rooms for the apartments on the upper floors. In both types of ground floor apartments the problem of the low-pitched ceilings had to be tackled. This was done in various ways. In the patio-apartments the ceiling height of the ground floor has been partly increased by cutting out the existing floors, and replacing them by a new concrete insulated floor fitted 0.20 m lower. In this part, the two bedrooms are situated. The ceiling height of the bathroom and the entrance hall remained unchanged. A new living room and a kitchen were created in an addition. This addition has a ceiling height of 3.20 m to compensate for the apartment’s low lie. The patio situated between the original building block and the new addition has been made accessible from the living room and the kitchen as well as from one bedroom and the hall. It has been given a back-entrance to the street behind the building blocks. See figures 7a and b for the floor plan and a vertical intersection of this dwelling type.
Figure 7a and b. Floor plan and vertical intersection of a patio-apartment located on the Siersteenlaan.
156
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands
In the two-floor garden-apartments the problem of the low-pitched ceilings has been tackled in a different way. Here, the second floor has been partly taken out to create a living room that is partially two storeys high. These living rooms have been enlarged by a 2.5 m deep addition at the back of the building. On the second floor of these garden-apartments there is a total of three bedrooms, an open space that can be used as a study or a play area, and a bathroom. See figures 8a and b for the floor plan and a vertical intersection of a garden-apartment. Since the structure is very hard to adapt in this building system, the number of changes has been reduced to a minimum. In the floor plan of the ground floor of the garden-apartments for instance, is the original wall of the stairwell still present in the enclosure of the kitchen. See figures 8a and b for the floor plan and a vertical intersection of a garden-apartment.
Figure 8a and b. Floor plan and vertical intersection of two-storey garden-apartment on the Siersteenlaan.
On top of the additions at the back of the building block, the new galleries for the upper floor apartments have been constructed. Between the galleries and the façades is an open space of 1.5 m deep to enhance the privacy and improve the daylight. See figures 8b and 9. Bridges spanning the space between the galleries and the building block connect the galleries to the original entrance halls.
Figure 9. Gallery access to upper floor apartments on the Siersteenlaan.
After renovation the total number of dwellings is 105, which is quite comparable with the original number of 108. After renovation however, all apartments have either their own front door on the street or they have elevator access. Apart from the nine two-storey ground-floor dwellings, now all apartments are 0-step, while before renovation there were no 0-step dwellings at all.
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands
157
Figure 10. Renovated façades on the Siersteenlaan.
Because of the actions ascribed above, the housing stock is now in accordance with the nowadays demands of various types of households like families with small children or elderly couples. To establish even more diversification in households, a mix of social housing with privately owned housing stock has been created by selling off all renovated ground floor apartments, while all the upper floor apartments continued to be let out as social housing. 2.5 Description of works In this project, more diversity in dwelling types was created by making large one- and two-floor apartments. The existing store-rooms on the ground floor were converted into living quarters. The ceilings on the ground floors had a limited height of only 2.42 meter, which means 0.18 meter short of the minimum height as required for living quarters. On the lower floors two different types of dwellings were realized: patio-apartments and garden-apartments. In both types of ground floor apartments the problem of the low-pitched ceilings was tackled in a different way. 2.5.1 Patio-apartments In the three larger building blocks new single-floor patio-apartments were created by adding a living room and a kitchen behind the building blocks in a new addition, separated from the original block by a private patio. These additions were entirely built on a new foundation. See the construction plan of the ground floor in figure 11. In the patio-apartments the ceiling height of the ground floor has been partly increased by cutting out parts of the existing ground-floors with a diamond sawing machine. These floors were replaced by a new concrete insulated system-floor fitted 0.20 m lower. These floors are suspended between the existing foundation beams, resting on L-shape steel profiles connected to the beams with chemical anchor-bolts. See detail 6 in figure 11. The recess due to the sawing of the original floor was used to fit light gypsum board walls, which were added on the inside of the existing walls of the sleeping rooms to improve sound insulation. A problem that had to be dealt with was the loss of lateral stability. Due to the removal of longitudinal internal walls the stability was reduced. To solve this problem new stability walls were built on the ground floor. New steel foundation poles were drilled trough holes in the ground floor. On top of the ground floor a concrete beam was poured, connected to the poles. Between the beam and the ceiling a strong brick wall was fitted. This combination of new building elements provided the desired addition stability. See detail 2 in figure 11. The new façades of the buildings required contemporary standards for thermal isolation. The existing outer cavity-walls were removed and replaced by a new brick wall, built on the outside of the existing foundation beam. The increased cavity was wide enough to accommodate the required thermal isolation. See detail 3 in figure 11 (drawing without the applied insulation).
158
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands
Figure 11. Construction plan and details of the ground floor of the patio-apartments.
2.5.2 Garden-apartments In the three smaller blocks the apartments on the 2nd floor were joined with the store-rooms on the ground floor to create two-floor apartments. In these two-floor garden-apartments the problem of the low-pitched ceilings has been tackled by partly taking out the second floor, to create a living room that is partially two storeys high. See figure 8 a and b and figure 12. This could be accomplished by removing the prefabricated concrete floor-elements, spanning between the transversal walls. See figure 4. Because the slab floors are incorporated in the structure with poured concrete (a so called wet joint) the removal of the floors had to be executed carefully. The living rooms have been enlarged by a 2.5 m deep addition at the back of the building. These additions were built on a new foundation. This foundation is connected to the existing foundation with chemical anchors. See the construction plan of the ground floor in figure 12 and the construction details 13 and 14. The floor is an insulated system of small prefabricated prestressed concrete beams and polystyrene insulating elements, finished with a concrete layer. The existing floors are insulated from the underside with a spray-method. This was possible thanks to the accessible space under the existing floors with sufficient height.
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands
159
Figure 12. Construction plan of the ground- and second floor of the garden-apartments.
Figure 13. Construction detail of floor addition
Figure 14. Detail of new floor construction
2.5.3 Top-apartments Elevators have been added to make the remaining smaller apartments on the upper floors accessible for everyone. The existing stair entrance system of the apartments (with stairs giving entrance to two joining apartments on each floor) had to be changed in a gallery entrance system. The galleries for the upper floor apartments are resting on new steel structures, supported by a new foundation pile or constructed on top of the additions at the back of the building blocks. See figure 14. Between the galleries and the façades is an open space of 1.5 m deep to enhance the privacy of the apartments and to maintain the access of daylight. Bridges spanning the space between the galleries and the building block connect the galleries to the original entrance halls.
160
Case study Siersteenlaan, Groningen - Vinkhuizen, The Netherlands
Figure 14. New galleries for the access of the upper floor apartments, supported by a new steel structure.
3 CONCLUSION In this renovation project many objectives had to be fulfilled. By dividing the three large building blocks into six smaller ones and creating passages between the dead-end streets and the Siersteenlaan the architectural appearance of the building blocks has greatly increased. The goal to increase the attainability of the shopping centre located opposite the Siersteenlaan and social control in the street behind the apartment blocks was accomplished. Other objectives, more diversification in dwelling types suitable for various types of households and a higher average functional quality, were obtained by creating large one- and twofloor apartments on the lower floors and by adding elevators for the remaining smaller apartments on the upper floors. The store-rooms on the ground floor were converted into living quarters. In this project the problem of the limited height of the store-rooms on the ground floor was solved in an inventive and appealing way. By making as little changes to the structure as possible, the diversification was made in a very cost-effective manner. Because all objectives were determined in dialogue with the tenants, there was good support for the interventions. This exemplary project can make all the involved parties proud on the reached result. REFERENCES Elk, R.S.F.J.van,and H.Priemus, Niet-traditionele woningbouwmethoden in Nederland, Stichting Bouw Research, 1971, Rotterdam Stichting Architectuur Lokaal, Veertig jaar later, vernieuwing van de wederopbouwwijken, Uitgave: stichting Architectuur Lokaal, april 2004. ISBN 90-802364-8-9 Jaarboek Architectuur in Nederland 2003-2004, Uitgave: NAi Uitgevers Rotterdam, 2004. ISBN 905662-370-2
Adaptations and Improvements on a Refugee Estate in Cyprus Ch. Efstathiades Faculty of Engineering, Aristotle University of Thessaloniki, GR-54124, Greece G. Hadjimichael Ministry of Interior, Town Planning and Housing Department, Lefkosia, Cyprus P. Lapithis Intercollege, Design department, Lefkosia, Cyprus
ABSTRACT: The worst housing problem ever faced by Cyprus appeared after the invasion of 1974 when 38% of its territory was occupied by Turkish military forces. At that time 36,2% of the housing stock was lost and therefore 200.000 refugees had to be settled in the rest of the island. Until 1986 the Government of Cyprus managed to house nearly 50.000 of these people in various refugee estates, according to an intensive housing program. Out of this number, approximately 30% have been settled in multi-story family houses. Today 20-25 years after that ¨housing boom¨, and due to the specific technical, environmental and seismic conditions in Cyprus, as well as the change of the quality of the available building materials, many of these multi-story buildings face a variety of problems. The solutions decided vary from complete demolition to plain painting.
1
GENERAL DESCRIPTION OF THE CASE STUDY
There are nowadays about 65 function able refugee estates, situated all over Cyprus, accommodating approximately 14000 housing units and more than 30000 people. There is no specific data concerning maintenance, renovations, modifications etc. of building envelopes. Indicative data however suggest that the average Cyprus family does not pay a lot of attention on these matters, that people extent as long as possible the various works needed and that they proceed to the necessary works, only when the performance of their building is intolerable, or dangerous looking always for the absolute minimum expense. The Government refugee estate ´´Arbishop Makarios III´ is situated in Limassol town, just 3.5 Km from the central area. It comprises two phases (Fig.1 and 2). The first one was build in 1979-80 and the second in 1984-86. It has a total number of 378 housing units, out of which 138 are apartments in three - storey family houses built during the first phase.
Fig. 1: Limassol Local Plan area and ´´Arbishop Makarios III´´ refugee estate Fig. 2: The site plan showing the 1st phase on the west side and the 2nd on the east Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved.
Adaptations and Improvements on a Refugee Estate in Cyprus
162
Buildings followed a simple ´´cubic form´´, for functional, economical and practical reasons. No efforts for differentiations were made during the primary construction phase. All the multistory buildings of the estate followed the typical flat slabs concrete structure, filled with plastered bricks. The layout of the Government refugee estate tried to safeguard the minimum through traffic. Some sort of youth anti-social behavior was spotted in the area. It is believed that due to the various community land uses incorporated in the greater area, the renovation program, and the gradual integration of the estate in the surrounding urban fabric, the area will share more happy days. The reconstruction of the buildings was based on typical and conventional techniques and materials. Some effort was made during the renovations in order to differentiate the buildings between each other.
2 2.1
PROBLEMS CONCERNING THE STRUCTURE Typology of the structure
In situ reinforced concrete, from foundations to the roof applies for the vast majority of the housing constructions (Fig. 3,4,5,6 and 7).
Fig. 3: A completely renovated building and a new one in the same refugee estate Fig. 4: The typical 2 and 3 bedroom flats
The typical filling of multi-story family houses comprises of brick walls (20 or 25 cm for the outer walls and 10 cm for the inner walls) which are plastered with 2-2,5 cm on either side. The finishing surface is usually covered by sprits or paint.
Adaptations and Improvements on a Refugee Estate in Cyprus
163
Fig. 5: View of typical refugee estates buildings
Fig. 6: Elevations and Sections Fig. 7: Foundation plan
2.2
Problems
All the multi-storey family houses of the chosen, by Action C16 period, were built before the adoption of any seismic regulations. Therefore their seismic behaviour is rather unknown and only special studies can reveal aspects of their performance. All the buildings built before the late 80´s, may sometime in the future, face possible seismic failure since at that time preliminary regulations concerning the calculation of seismic loads were issued whereas construction regulations were adopted in the beginning of the 90´s. The vast majority of ‘’multi-story resident buildings’’ in Cyprus were built according to typical conventional methods (reinforced concrete for the bearing system, brick walls and plaster finishing). Although a considerable number of seismic excitations appear during the life of all the structures in Cyprus only a very small number of buildings showed serious damages. The main loads that are acting on the buildings are: Vertical - Dead and Live loads Horizontal - Earthquake load
Adaptations and Improvements on a Refugee Estate in Cyprus
164
In Cyprus there are no any problems or any cases concerning landslide loads or subsidence mining loads. Moreover there are no special regulations dealing with exceptional loads such us explosions. So, these loads are not taken into account for the structural analysis of the building. Furthermore since reinforced concrete is used from foundations to the roof, the structure is very heavy and therefore the wind and fire loads are not critical, so there are not calculated. The thermal and acoustic insulation of the buildings were almost inexistent. 2.3
Actions
Depending from the condition and the level of damage of each building of the refugee estate, a different technique is adopted ranging from simple maintenance to total demolition. So the possible decision for a certain building was one of the following: Total demolition Simple maintenance Complicated maintenance and improvements 2.4
Description of works
2.4.1 Demolition The level of damage for some of the buildings was very high. For those buildings, a financial investigation was estimated that the cost of the necessary improvements was more than the cost for the constructing of a totally new complex with the same number of housing units (Fig. 8). Moreover in some cases extra free space for the refugee estate was needed, in order to improve the quality of life for the residents of the nearby complexes. Concerning the above , demolition was decided for a number of buildings.
Fig. 8: Total demolition was chosen for some of the buildings
2.4.2 Simple maintenance Some of the three story’s residential buildings of the refugee estates, the newest one’s, needed only simple maintenance. In most of these cases the respective improvements were related only to the painting of the buildings, for aesthetic purposes or combining asphalt layer with painting on the roof, in order to achieve better moisture and thermal insulation. The main achievement of this kind of maintenance is that energy performance was improved since less energy is needed for cooling and heating the buildings.
Adaptations and Improvements on a Refugee Estate in Cyprus
165
Fig. 9: Roof finishing with asphalt layer and reflective paint Fig. 10: Rotten reinforced concrete
The combination of asphalt layer with reflection painting for the roofs (Fig. 9) can be adopted for any kind of building with concrete roof slab. It’s a simple kind of maintenance with shortterm effects, since the results are immediate introduced just after the technique is adopted. In some other cases the maintenance was limited only to the repairing of the rotten concrete of the structures (Fig. 10). 2.4.3
Complicated maintenance and improvements
In many cases the necessity for more complicated maintenance appeared. The needs were classified to: Structural aspects Architectural and Functional aspects Social and cultural aspects Economical aspects 2.4.3.1 Structural aspects - The load bearing structure Most of the buildings of the refugee estate needed a different type of improvement, depending on their condition (Fig. 11). The common types of renovation we re: Repair of damaged structures (without upgrading their structural capacity) Repair and strengthening of damaged structures (including upgrading of the seismic capacity of the building) Strengthening of the existing structures (including upgrading of the seismic capacity of the building and foundations) Additions of structural elements Removal of unnecessary loads
166
Adaptations and Improvements on a Refugee Estate in Cyprus
Fig. 11: During the renovation and after the completion of the works
(a) Improvement of the columns – seismic upgrading of the building The columns of the building have overpass the maximum bearing capacity codes due to: poor construction materials more loads than those they could afford The solution adopted was the upgrading of the structure, by increasing its load bearing resistance. This way the service life of the building was extended by 20-30 years and the safety of the structure against gravity and earthquake loads was increased. The certain technical solution can be adopted for buildings with heavy or light concrete column envelope. There is no serious effect in the architecture of the building since no extra parts are added to the structure. The only effect to the building is the slight increase of the dimensions of the columns (Fig. 12, 13, 14 and 15).
Adaptations and Improvements on a Refugee Estate in Cyprus
Fig. 12: Technical details for reinforcing existing columns and walls
Fig. 13: Technical details for reinforcing existing columns Fig. 14: Reinforcement of a corner column
167
168
Adaptations and Improvements on a Refugee Estate in Cyprus
Fig. 15: Reinforcement of an inside column
(b) Improvement of the foundation of the buildings A more extended improvement of the structural stability of a structure was, together with the improvement of the columns, the upgrading of the foundation of the building. For this purpose larger footings and also stronger connective beams were constructed (Fig. 16 and 17).
Fig. 16: Reinforcement of foundations connecting beams Fig. 17: Foundations before and after
(c) Deflection - Serviceability problems In many cases, mostly in cantilevers and rarely in the inner slabs the deflection of the slabs excited the limits of serviceability due to poor materials or more loads than they could overtake (extreme loads compared with the design ones). Two different methods were adopted: Addition of extra supports to reduce deflection (Fig. 18, 20 and 21) Removal of unnecessary loads (Fig. 19)
Adaptations and Improvements on a Refugee Estate in Cyprus
169
Fig. 18: Adding of a new column
In every case where that was possible, the second method was adopted, since that way there was the advantage that the total weight of the building was reduced, leading also to less seismic loads. A lot of unnecessary loads, like surrounding walls on top of the buildings or balconies, were removed.
Fig. 19: Removal of any unnecessary loads from the building (surrounding walls on roof and balconies) Fig. 20: Metal support for balconies Fig. 21: Dangerous balconies and metal support (before and after)
170
Adaptations and Improvements on a Refugee Estate in Cyprus
2.4.3.2 Architectural and functional aspects During the renovation process an effort was made, to differentiate the buildings and to give different characteristics to each other, in order to be easily distinguished (Fig. 22 and 23). Moreover appropriate arrangements were adopted for handicapped people, in an effort to improve the quality of life in the estate.
Fig. 22: A typical building in a refugee estate and typical interventions by the residents to gain some space Fig. 23: Reconstruction of a staircase roof
All damaged or old pipes and wirings were changed with new ones. The easiest and best way, from the financial point of view, was to sidestep all the existing works and install new external and exposed piping and wiring (Fig. 24).
Fig. 24: No special tracking for wiring. New arrangements were fixed externally (exposed) on the building envelope
Adaptations and Improvements on a Refugee Estate in Cyprus
171
2.4.3.3 Physical aspects For the time being and although there are technical recommendations for thermal, acoustic, light and fire performance for new buildings, there is not any legal obligation for the designers to comply with any rules or recommendations. In most cases, good environmental conditions are achieved by using (“external” energy consuming mechanical methods) like air-conditioning systems or split units. In the refugees estate there was not any introduction of such interventions and the only improvement was the replacement of old wooden windows with double glazing aluminium systems (Fig. 25).
Fig. 25: Substitution of all wooden doors and windows with new aluminium frames
2.4.3.4 Accessibility Different social problems appeared in multi-story buildings and in the overall site of the Government refugee estate. The bigger problem was some sort of ‘’isolation and identity problem’’ due to the non-penetrative road network of the estates and the patterned morphology of the buildings. Also some of the first estates built in the 70’s, present some sort of anti-social youth behaviour. The problem was overcome through the overall redesign of the renovations, the reimbursement of public open areas of the estate (squares etc) and the improvement of other common parts of the buildings (entrance, staircase etc).
3
REFLECTIONS
From all the above the following conclusions are worth to be mentioned: The construction safety was the main issue of this case study. The vast majority of the renovations were related to the construction safety and the stability against earthquake actions. A lot of unnecessary loads, like surrounding walls on top of the buildings or balconies, were removed. Only conventional techniques were adopted and no efforts for use of FRPs or other modern methods were made. No specific studies were carried out concerning the building physics. There is no doubt that the general living conditions have been improved a lot. However newly installed air–conditioning units can be seen on some renovated buildings. This indicates that expensive renovations are not doing miracles in a problematic old housing estate. The average construction cost of the estate (according to 1979 values) was 75 C.P./m2 (about 130 Euro/ m2 ) whereas the renovation cost (according to 2003 values) is estimated to reach 100 C.P./m2 (about 170 Euro/m2). There is no doubt that direct comparisons may be misleading and that feasibility studies carried out so far, had already taken into account the inflation rate, the
172
Adaptations and Improvements on a Refugee Estate in Cyprus
cost of living and the final result achieved. Having this in mind it can be stated that the renovation of the structure and infrastructure undertaken was worthwhile and that the living conditions of the inhabitants have been improved substantially. It is believed furthermore that the work carried out in the above-mentioned estate, can well fit within the sustainability approach.
REFERENCES Government of Cyprus 1996. Streets and Building Law (Cap. 96). Lefkosia: Government of Cyprus Government of Cyprus Immovable Property Law (Tenure, Registration and Evaluation – Chapter 224). Lefkosia: Government of Cyprus Government of Cyprus 1972 . Town and Country Planning Law (Law 90/72) Lefkosia: Government of Cyprus Government of Cyprus 1985. Municipalities Law (Law 111/85). Lefkosia: Government of Cyprus. Ministry of Commerce 1998. CYS 98, Cyprus Organization for Standards and Control of Quality. Lefkosia: Government of Cyprus Statistical Service 2001. Population Census. Lefkosia: Government of Cyprus Government of Cyprus 1992. Regulations for seismic loads in Cyprus. Lefkosia: Government of Cyprus ȅASP 2000. Recommendations for pre-seismic and post-seismic building interventions. Athens: Greece
Externally Bonded Steel or Carbon Fiber Reinforcement Filip Van Rickstal, Wine Figeys, Kris Brosens, Dionys Van Gemert Faculty of Civil Engineering, Katholieke universiteit Leuven, Belgium
ABSTRACT: Externally bonded reinforcement offers a strengthening method that enables to solve different frequently occurring problems for the structural frame of the multi story, multi family buildings. The technique can be useful when applying often used interventions such as the removal of supporting walls or supporting columns. It is a technique that can easily be applied to the concrete beams and columns as well as to the concrete floor slabs. This paper explains the basic principle of the technique and discusses two case studies to show the possibilities of the technique. 1 INTRODUCTION Externally bonded reinforcement offers a strengthening method that enables to solve different frequently occurring problems for the structural frame of the multi story, multi family buildings. It is a technique that can easily be applied to the concrete beams and columns as well as to the concrete floor slabs. For that reason the technique allows important architectural freedom by allowing the enlargement of rooms and the removal of supports. 2 TECHNICAL PERFORMANCE 2.1 Structural integrity The basic principle of the technique is very simple. It essentially consists of bonding external reinforcement to the concrete structure for carrying tensile forces and thus to enhance the load bearing capacity (Fig.1). The external reinforcement materials are mostly either steel plates or fibre reinforced composite materials such as carbon fibre reinforced polymers (CFRP), glass fibre reinforced polymers (GFRP) or aramid fibre reinforced polymers (AFRP). The tensile properties of the fibre reinforced materials are only available in the fibre direction. Externally bonded reinforcement can be used for strengthening, repairing and stiffening of all kind of structures: evidently concrete structures, but also masonry and even wooden structures.
Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved
174
Externally Bonded Steel or Carbon Fiber Reinforcement
Fig. 1 Retrofitting of concrete structures (Ninove Belgium, 1994)
2.2 Possible Reasons for Applying External Reinforcement Without discussing the different causes, a list of possible raisons to apply externally bonded reinforcement is given: calculation errors execution errors changes in exploitation use Three main groups of causes may lead to the use of externally bonded reinforcement, figure 2: users, constructors and environmental conditions and disasters. The increase of the load bearing capacity, the removal of a load bearing wall and the change in destination are typical examples of causes induced by the users. Also bad maintenance often leads to additional repair work, which might be done by externally bonded reinforcement. The second group of causes is linked with mistakes or faults by the constructors. Possible reasons are: bad design, poor workmanship and low quality of the used materials. The third group of causes contains the damage induced by environmental conditions or disasters. This kind of damage is sometimes very difficult to exclude, e.g. damage due to fire, explosions and earthquakes.
Fig. 2 Schematic overview of causes to use externally bonded reinforcement
Externally Bonded Steel or Carbon Fiber Reinforcement
175
2.3 Fire protection An important issue is the very poor fire resistance of bonded systems. Since the glass transition temperature of the commonly used thermosetting adhesives varies between 35°C and 95°C, the heat development in case of fire implies a real danger for the stability of the strengthened structure. The heat does not cause thermo sets to melt and flow, but it does induce some softening and possibly significant changes in properties as Youngs’ modulus, creep, strength and chemical resistance. Especially the fire resistance of bonded steel plates is problematic, due to their high thermal conductivity. When a considerable fire resistance, often prescribed by standards, is required, a heat insulating cover will be necessary. This insulation will provide enough time for the users of the structure to get evacuated in case of fire. 2.4 Other aspects of technical performance, durability Since this technique is a purely structural measure to solve the lack of load bearing capacity of concrete beams and concrete floor slabs that is applied inside, the technical solution is very durable and long-lasting. 3 NON-TECHNICAL ASPECTS 3.1 Functional and social performance The technique of externally bonded reinforcement meets very well the requirements for visual and architectural comfort and is therefore very suitable to be used for retrofitting of urban building envelopes. Especially the use of FRP offers a wide variety of applications. Only minor changes in the dimensions of the structural parts are needed which assures the original outlook of the construction, whereas the structural consolidation is guaranteed. However, a good insight and competence of the design engineer is indispensable to make an appropriate restoration and renovation possible. The technique could enable to remove supporting columns and to enlarge the free living space conform to the contemporary architectural praxes. The technique can bring floor slabs into the safety level required by current standards. 3.2 Economical performance The technique of externally bonded reinforcement requires a skilled team. The surface preparation is labour-intensive and the manipulation to position the steel plates is a time consuming task. In case of CFRP, the material cost is quite elevated. All these factors make the technique costly, but still affordable. Compared to the more traditional way of strengthening structural parts, the overall cost is still lower and the functional performance is better. 3.3 Environmental performance From an ecological point of view the technique limits the use of resources. No destruction and replacement of the existing (concrete) structures and hence no ecological cost in terms of cement and granulates consumption to produce the replacing parts. The energy cost and the resource consumption of the used materials are only a marginal part of the overall cost. 3.4 Conclusions To summarise: the economical cost might be comparable to the cost of other techniques; the ecological cost however is definitely lower than the ecological cost of traditional techniques. Buildings from the seventies or sixties often don’t meet the current safety prescriptions for the load bearing parts. By applying external reinforcement they might do.
176
Externally Bonded Steel or Carbon Fiber Reinforcement
4 CASE STUDY: STERREVELD IN WEZEMBEEK-OPPEM, BELGIUM Figure 3 shows the apartment building Sterreveld in Wezembeek-Oppem in Belgium. The apartment is completely renewed. The façade is removed and upgraded. The layout of the individual plans is completely changed; load bearing walls are removed etc… This case study will only shortly discuss the application of externally bonded CFRP to both the concrete floors slabs and the concrete beams. Other aspects of the renewing are not discussed here.
Fig.3 Sterreveld in Wezembeek-Oppem, Belgium
The reinforcement of the floor slabs is insufficient. As a consequence, the floor does not meet the current standards about safety and load bearing capacity. To overcome this problem, CFRPstrips were glued to the ceiling at each story. The lack of load bearing capacity with regard to bending was limited and therefore it sufficed to glue narrow strips to the concrete in the middle of the span as shown on figure 4.
Externally Bonded Steel or Carbon Fiber Reinforcement
177
Fig.4 Narrow CFRP-strips are glued to the concrete in the central zone
The second application in this case study is the need for extra shear strength in the concrete beams. Figure 5 shows the application of that kind of external reinforcement as well as the longitudinal reinforcement to enhance the bending capacity.
Fig.5 The steel plates in the bottom centre zone increase the bending strength, whereas the carbon fibre stirrups increase the shear resistance of the beam
178
Externally Bonded Steel or Carbon Fiber Reinforcement
5 CONCLUSIONS The application of external reinforcement allows the architect to apply popular interventions such as the removal of a load bearing wall of supporting columns without reducing the height of the rooms. Metal sheets and CFRP-sheets are applied frequently. The technique is illustrated by two common cases: strengthening of floor slabs and increasing the load bearing capacity of beams by shear strengthening and bend strengthening. Similarly, the technique can be applied for cantilever balconies. REFERENCES Brosens K. (2001), Anchorage of externally bonded steel plates and CFRP laminates for the strengthening of concrete elements, PhD thesis, K.U.Leuven 2001 Van Gemert D., Brosens K. (2003), Non-metallic reinforcement for concrete structures, Journal of Materials - Design and Applications, 2003 O.Ahmed, D.Van Gemert, L.Vandewalle (2001), Improved model for plate-end shear of CFRP strengthened RC beams, Cement and Concrete Composites 23 (2001), pp.3-19. K. Brosens, D. Van Gemert & S. Ignoul (2001), Strengthening of concrete structures with externally bonded steel plates or CFRP laminates - Part II: Innovative applications, WTA International Journal for Restoration of Buildings and Monuments, Aedificatio Verlag, 2001, Heft 7, pp. 539-556 Van Gemert D., Ignoul S., Brosens K. (2004) Strenghtening of concrete constructions with externally bonded reinforcement: design concept and case studies, IMTCR 2004 innovative materials and technologies for construction and restoration, University of lecce, Italy, June 6-9
Balconies, Loggias and Different Thin-walled Units in Large Panel Buildings K. Wróbel & W. Kubiszyn Rzeszow University of Technology, Rzeszow, Poland
ABSTRACT: After 45 years of use without repairs, serious damage of elements of multi-flat apartment buildings is generally observed. In buildings exploited for about 25 years, the effects of corrosion of thin reinforced concrete elements (balconies, loggias, roofs above entrances to buildings and architectural details) are common. Errors in design, realization and maintenance represent a source of the damage. The paper presents an actual technical state of these elements taking as an example balconies, loggias and the range of their rehabilitation as well as current ways of the surface protection of repaired elements. From the economic point of view it is profitable to connect the rehabilitation of thin reinforced concrete elements, complex repair of buildings and thermo renovation of external walls.
1 INTRODUCTION In multi-flat apartment buildings exploited for almost forty five years without repairs very serious problems come into being. They concern durability in general, and that of thin-walled units subjected to atmospheric factors in particular. These problems become more serious due to the fact that during their building process the durability was not valued enough. What mattered in the past was to assure the minimum level of safety. During the investment process, the only criterion taken into consideration was the cost of building the object. The working expenses and assurance of usable efficiency were not analyzed. In buildings exploited for about twenty-five years problems with the durability of external thin-walled units are quite common. 2 ANALYSIS OF TECHNICAL STATE OF STRUCTURE OF RC THIN-WALLED UNITS The analysis was based on 1998-2005 comprehensive assessment of the technical state of the 11 - storey buildings exploited for almost forty five years as well as the opinion of the technical state of balconies in the buildings of 3 - 5 and 10 - storey exploited for about twenty-five years. They were the buildings of the building societies in Rzeszow. Based on that opinions, the range of repairs and their designs were determined. Carrying out these works was also supervised. The thin-walled elements of the multi-flat buildings particularly exposed to weather conditions are the balconies of different shapes and structures, loggias, roofs above the entrances to the buildings and every unit of the architectural detail character (over one thousand of them were estimated). Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved
180
Balconies, Loggias and Different Thin-walled Units in Large Panel Buildings
Buildings to be estimated contained balconies of different structures and dimensions. The present article has limited itself to investigating three types of them: cantilever balcony plates of different dimensions (Fig. 1),
Figure 1. Examples of corroded cantilever balconies
balcony plate of 2.4 m x 1.8 m with a reinforced concrete supporting structure consisting of an arterial column and a cantilever beam supporting the plate (Fig. 2),
Figure 2. Examples of corroded balconies supported with the reinforced concrete structure
balconies being a combination of the two types of the balconies mentioned above (Fig. 3). The actual technical state of the balconies resulting from the piling up of many irregularities of all the phases of the investment process was estimated as very bad, just about failure or failure (some of analyzed balcony plates underwent failure).
Balconies, Loggias and Different Thin-walled Units in Large Panel Buildings
181
Figure 3. Example of corroded balconies being the combination of two types of structures
2.1 Designing disadvantages They are: designing thin balcony plates with a too thin concrete cover of reinforcement (~ 5 mm), without a proper insulation protecting against adverse weather conditions, the lack of the proper choice of finishing layers as well as finding the way of isolating the places especially significant from the durability point of view (connection of the balcony plate with the wall, balcony doorsteps, fixing balustrades in the balcony plates). The correct (elastic) protection against water of the dilatation break around the arterial column in the plate, as well as on the connection: wall – plate (in balconies with a reinforced concrete supporting structure). What is more, the balustrades closing the outflow of the water from the balcony surface were often designed. 2.2 Executive negligence Improper assembly (balcony plate slanting towords the building) is the cause of atmospheric sewage gathering by the building walls and its flowing into the building through the leaks and holes in the floors. Setting the flashing permanently or its lack, lack or an improper insulation of the upper plate surface against water, improper sloping grade of the upper surface and the side edges of balcony plates, as well as low strength of the concrete of some balcony plates are also responsible for the damage. Bad workmanship, i.e. filling the empty spaces for arterial columns of supporting structure in the poles as well as spaces between the beam supporting the plate and the plate itself by polystyrene, rubble, paper bags or leaving them without filling, also has a negative effect. 2.3 Exploitational negligence Exploitational negligence consisting in missing the current and major repairs is yet another factor. The negligence results in: the corrosion of flashing, fracturing and spalls of finishing layers made of mortar cement. Lowering the durability of the concrete of the whole plate or its units is the consequence of the lack of insulation against water and corrosion of flashing, spalls along the edge of the concrete, the corrosion of reinforcing; in balconies with opposite slopes it is par-
182
Balconies, Loggias and Different Thin-walled Units in Large Panel Buildings
ticularly dangerous because the reinforcing in the anchoring zone of the cantilevers corrodes the most intensely. Saline patches occur on the bottom surfaces of the plates (Fig. 1). The most intense lowering of durability was observed in the case of balconies covered with grape-vines and those whose surfaces were covered with plastic carpets which were moisture holding. The stages of the corrosion intensity were diverse (PN-88/B-01807). In almost all balconies the corroded concrete was coming off along their edges, pieces of concrete loosely connected with subsoil were visible as well as the timber blocks in the places of fixing balustrades in plates (and empty spaces being the result of their lack). Timber blocks left in the concrete of the balcony plates swelled accumulating moisture and cracked the concrete - in their surroundings the concrete corroded the most intensely. The columns and beams supporting the balcony structures underwent intensive corrosion in neighborhood of the passage of the column through the balcony plate as well as in the places were the reinforced concrete flower shelves were fixed to the column (Fig. 2). The outflow of water was made impossible due to the badly profiled surfaces of the top layers and the balustrades closing the front edges of the balconies (Fig. 3). 3 DIAGNOSTICS OF BALCONIES AND LOGGIAS STRUCTURES The proper estimation of the concrete strength and the technical state of the reinforcement during exploitation was difficult. The macroscopic estimation of the structure of the balconies indicated that their technical condition was very poor. The nondestructive estimation of concrete quality, in the situation when the concrete underwent corrosion and became superficially hardened in the result of surfaceable carbonatisation was not fully reliable. The finishing layer of the balconies as well as the flashing near the balconies’ door made the correct location of the reinforcement impossible. It was also impossible to determine the degree of the advanc of corrosion of RC in the most important place from the load capacity point of view – near the anchoring of the balcony in RC ring beam (the cantilever balconies), as well as in places of passages of columns through balcony plates (the balconies with the reinforced concrete supporting structure). In the situation in which the precast balcony plate is reinforced by two wire meshes of a similar distance of bars (upper and bottom), the location of the upper armature without destroying the finishing layers while making use of the available equipment is not possible with the usage of the equipment accessible to the authors. The emergency state of the structure was indicated by the visibly corroded bottom and/or upper reinforcement in balconies without a finishing layer. Moreover small pieces of concrete were coming off along the edges of the plates after being slightly hit, which caused a serious threat to people being in the vicinity of such buildings (especially eleven-floor buildings). On the basis of the sclerometric investigations of concrete in the neighborhood of anchoring the balcony plates in RC rings, a large range of the concrete strength was noticed. There was C 16/20 concrete, as wall as out of class concrete. At the investigation of the stage of the concrete coating neutralization. The reinforcement in the plates showed pH < 9, which indicates the lack of anticorrosive protection of concrete in relation to steel. The final and comprehensive estimation of the technical state of the balconies was possible only during the repair after the finishing layers had been removed. At that time according to code PN-88/B-01807, the proper diagnostic estimation of the state of the balcony structure was carried out aiming at determining the advance of the concrete cover corrosion and the size of the corrosive decreases of the reinforcing bars. Additionally, the static calculations for the real properties of the materials and dimensions of the elements were conducted, which permitted establishing the stages of usefulness of the analyzed structures for further exploitation. The various damage of balcony structure was determined - degrees III and IV prevailed. However, a part of the analyzed structures of the balcony plates were worn out up to degree V.
Balconies, Loggias and Different Thin-walled Units in Large Panel Buildings
183
4 THE CHOICE OF REPAIRING AND STRENGTHENING METHODS Various ways of repairs of a structure were accepted, according to code (PN-88/B-01807). In the case of the balcony and loggia plates and units of supporting structures worn out in III and IV degree, the repair works were preceded by removing the corroded concrete (Fig. 4), cleaning the corroded reinforcement to Sa 2 1/2 degree of purity as well as cleaning and moisturizing the concrete. In the case of the balconies with a reinforced concrete supporting structure (Fig. 2), the diagnostics and repairs were also carried out for the arterial columns and beams supporting the plate. To provide the proper structural work around the column and at the wall-balcony connection an elastic dilatation tape was applied. The decision about the amount of concrete to be removed was made during the repair works. The removed concrete was a strip of minimum 10 cm wide along the edges of the balcony. In several cases it was decided that the total removal of the corroded concrete was necessary. The concrete was also removed totally when the reinforcement showed the signs of intensive pitting or extensive superficial corrosion. Two technologies of repair were applied depending on the size of the corrosion losses of the concrete. The repair of small decreases of plates (up to 5 cm of depth) was executed with the use of ready-made PCC preparations. Larger decreases were filled with concrete modified polymer emulsion. In every case before connecting the old material with the new one, the connecting layer was made.
Figure 4. The view of balconies prepared to repair
In the case of balcony plates which underwent a failure of V degree, an additional supporting steal structure was applied (Fig. 5) which was always adjusted to the type of a balcony structure. In buildings with balconies as cantilever plates, in which the concrete of the reinforced concrete ring beam was of good quality and where there was total corrosion of the reinforcing bars near the balcony doors, the corroded reinforcement was replaced by gluing in RC ring beam bars by means of HILTI anchoring mortar. This anchoring mortar was a synthetic resin based on methacrylate. The works were in each case preceded by testing the pull out resistance of the bars glued in the RC ring beam by means of the mortar. In each case, the break of a bar followed (even if the concrete of the ring beam was C12/15 class). The balustrades cutting off the outflow of storm sewages from the surfaces of the balconies were replaced with the new ones with a bottom clearance of a minimum 10 cm (Figs 3 and 7). After carrying out flashing and cement screed (also modified by polymer emulsion), the reinforced concrete structure of a balcony is under the same influences which caused its damage.
184
Balconies, Loggias and Different Thin-walled Units in Large Panel Buildings
To maintain balcony usability as long as possible, it is necessary to cut off the influence of unfavuorable atmospheric factors. It can be done in several ways. The two of them used most often are listed below (Fig. 6): Protection of balcony surfaces by epoxy resin with quartz sand in colour adjusted to the colour of the facades - this solution was adapted from bridge protection solutions. To prevent the surface of epoxy resin from discolouring, it was covered by a film resistant to ultraviolet. Protection of cement screed surface by an elastic insulating slime based on cement. The top layer of the balconies was covered by ceramic frost-proof tiles.
Figure 5. Supporting structure of balcony plate
Figure 6. The cross section of a balcony after repair
Balconies, Loggias and Different Thin-walled Units in Large Panel Buildings
Figure 7. The view of façades after repair
185
186
Balconies, Loggias and Different Thin-walled Units in Large Panel Buildings
5 SUMMARY Designing without taking into account the requirements of usable durability, executive negligence, long-term unfavorable weather conditions, lack of proper superficial protections lead to advanced corrosion of concrete and steel, especially thin-walled units. They need repairing. The choice of the repair system is made after considering the sequence of factors. The most important of them are: the validity of a unit from the structural point of view, the kind of loads and environment conditions in which the structure is to work, the physical - chemical properties of structural material, expected durability of repair. Supporting of structures is necessary in many cases. Those works are then labour-consuming and expensive. Thanks to new technologies, full restoration of the usability efficiency of repaired units and their maintenance is possible. The superficial protection of concrete after the repair is necessary. Connecting the repairs and strengthening thin-walled units (balconies in particular) with repairs of the whole object and termorenovation of external walls is justified from the durability, esthetics and cost points of view (the cost of scaffoldings in comparison with the cost of repairs of the whole building is significant). The total repair also eliminates doubling of some works. Running some works with the use of stationary scaffoldings provides a suitable technological regime. REFERENCES PN-88/B-01807 Anticorrosion protections in building. The concrete and the reinforced concrete structures. Principles of diagnostics of structures. Wróbel, K. & Kubiszyn, W. 1998 - 2005. Estimations of technical state of balconies in multi-flat building ... in Rzeszow. Rzeszow 1998-2005. Wróbel, K. & Kubiszyn, W. 1998 - 2005. Projects of repairs of multi-flat buildings ... in Rzeszow. Wróbel, K. & Kubiszyn, W. 2000. The emergency state of the reinforced concrete balconies in multi-flat apartment buildings. "The current Problems of Building and Environmental Engineering”, part.1 – Building; V Scientific Rzeszow - Lwow – Koszyce, Conference in Rzeszów: 591-598. Wróbel, K. 2002. Durability and strengthening of thin reinforced concrete elements in multi - floor apartment buildings. COST C12 - Working Group WG1 "Mixed Building Technology, N°: C12-WG102-31, Volos, Juni 14th 2002. Technical cards of systems ADDIMENT, POLYMENT, COMPAKTA, DEITERMANN, SIKA and HILTI.
Recycling Prefabricated Building Components for Future Generations C. Asam Institute for Preservation and Modernisation of Buildings at the Technical University of Berlin
ABSTRACT: This report is engaged in the current situation of the housing site in eastern Germany. The focal focus is on the measures to reducing the enormous number of empty dwellings. A re-use method is discussed as one option to the present demolition of vacant buildings. Thereby dismantled concrete panels were applied to build new, more effective demand houses.
1 STARTING POINT In 2001 the Federal Ministry of Transport, Building and Housing launched a nationwide assistance programme entitled ‘Stadtumbau-Ost für lebenswerte Städte und attraktives Wohnen’ (‘Urban renewal programme in the East: cities to live in and attractive residential accommodation’). Given concerns over low flat-occupancy rates in eastern German communities, the main objective of this programme was to provide immediate and integrative city planning. Demolition was designed to reduce the surplus of dwelling units. 350 local authorities applied, but out of these only 259 towns and 10 districts for Berlin were chosen to participate (Fig. 1). The results were presented in 2003. Among other criteria, an evaluation was made to gauge the possibility of permitting alternative re-use of the re-treated (reconverted) buildings in industrially prefabricated panel units.
2 RESULTS OF THE COMPETITION An examination of the potential re-utilisation of dismantled pre-cast components from dwellings in the former GDR shows that successful re-utilisation of these components depends on a multiplicity of factors. The first factor is the availability of appropriate components, which must be documented by housing type and specification. With regard to participating towns and local authorities, it is estimated that some 350.000 flats will have to be demolished by 2020.
3 RE-TREATING METHODS Another key factor is the re-treating method. The only dismantling method suitable will be one, which provides appropriate components of high quality, unlike the common method of complete re-treating (demolition), whereby all the components are damaged. An evaluation showed that 50% of dwellings would be completely re-treated (demolished) and some 14% would partially re-treated, while for the remaining 36% there was no decision about the method. Figures covering existing re-treating plans, however, demonstrate that there are already plenty of potential and sufficient quantities of dismantled components.
Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved
188
Recycling Prefabricated Building Components for Future Generations
Figure 1. Geographical overview of the competitors; the thin lines show the borders of the former GDR districts (source: IEMB).
Recycling Prefabricated Building Components for Future Generations
189
4 BUILDING TYPES The more or less 2.2 million flats built in ‘Plattenbau’ style exemplify the varieties of building involved; these can be classified in types with similar structures. This classification into types showed that type ‘WBS 70’ is over-represented, accounting for 67% of all re-treating cases.
Figure 2.
Re-treated building types.
5 PLANS FOR NEW BUILDINGS A guarantee must also be given that existing components will be used in types of housing for which there is a market demand, e.g. single or double occupancy houses. Quality of construction using recycled components in these cases must not be inferior to that of an entirely new building. Given the above conditions, the general situation in the large housing developments of the former GDR suggests a highly promising outlook, both in present and future. An evaluation of the re-treating scheme shows that the ‘Stadtumbau-Ost’ urban-renewal programme will have considerable prospects of success in the states of eastern Germany and will provide an enormous amount of recyclable construction material.
Figure 3. Intended new constructions in the re-treating areas.
‘Stadtumbau-Ost’ projects based on urban in-filling, densification principles and building in integrated areas will play a particularly key role. A large number of the local authorities taking part intend not only to dismantle buildings, but at the same time to construct new ones, featuring schemes for small-scale housing estates.
Figure 4.
Timescale for ‘Stadtumbau-Ost’ schemes (light-coloured line: re-treat) (dark line: new building)
190
Recycling Prefabricated Building Components for Future Generations
6 ECONOMIC AND ECOLOGICAL ADVANTAGES OF RE-UTILISATION The results of a commercial-viability study show a vast potential for savings in the ‘300’ group of construction costs (DIN 274, shell construction). Although this calculation was made within a secure feasibility level and using a worst-case scenario, it showed savings of 26% on total costs of building components. This includes a return on sales of the components equal to the costs of dismantling, despite the fact that no trade of this kind is currently underway. Established ecological benefits from the re-use of components – a positive balance in energy savings and reduced use of natural resources in the production stage – will be complemented by further economic effects, and as energy prices continue rising, so the outlook will improve.
Conventional construction (massive)
Primary energy in MJ/t
Recycling method
Global warming potential in kg CO2equivalent
Figure 5. Cost comparison.
Potential of acidification in kg SOx-equivalent
Figure 6. Ecological benefits, recycling components (left column), new construction (right column).
7 PRACTICAL PROJECT: ‘RECYCLED HOUSE’ ‘Das recycelte Haus’ (the Recycled House) was a prototype scheme developed from a research project entitled ‘Recycling prefabricated building components for future generations’, based on considerations of architecture and building. But economic and ecological benefits were also a central consideration in the construction of a prototype.
Recycling Prefabricated Building Components for Future Generations
191
The aim of the project was to test the potential for dismantling and design of a house permitting recyclable components. The shell construction consisted of recycled components obtained from current demolition projects.
8 DISMANTLING AND TRANSPORTATION Interior walls and roof components were mostly used for the prototype. The engineering experiment proved that the dismantling of ‘WBS 70’ provided high-quality components. Conclusions have also shown that the quality of dismantling can be influenced significantly by the technology applied. Hence, for instance, a hand procedure, using light chiselling machines, is more applicable than heavy-duty machinery (e.g. small excavator).
Figure 7. Partial dismantling of a ‘WBS 70’ a so-called ‘donor building’.
Figure 8. Left: Slab components being cleaned before the dismantling. Right: Dismantled interior wall.
Transportation must be carefully organised and proper storage must be assured.
Figure 9. Wall components transported in upright position.
9
Figure 10. Slab components transported in stacks.
QUALITY ASSURANCE (QA)
Once dismantled, the components lose their legal approval as construction material. Consequently an accompanying quality-assurance process is indispensable. For the prototype’ recycled house’, besides the experimental tests for the slabs, material trials were also conducted.
192
Recycling Prefabricated Building Components for Future Generations
The number and method of the trials depended mostly on the initial condition of the recycled components and could only be undertaken by a competent inspecting authority.
Figure 11. Sampling for concrete tests.
Figure 12. The slabs were tested both before and after dismantling and transportation. No evident changes in bearing capacity were identified.
The examination of ‘WBS 70’ provided high-quality results for material characteristics, ensuring that all the components for the prototype could be used. Measurements particularly included the following:
Carbonisation Concrete compressing strength Position of the reinforced steel Bearing capacity of components.
10 TREATMENT OF COMPONENTS Construction of a test building yielded some useful insights into how these elements can be rendered re-usable at a realistic cost. For this purpose an analysis was made of different types of concrete cuttings. New fixing constructions were also tested. It also proved possible to create buildings, which deviate from the original construction grid.
Figure 13. The components are stored until treatment.
Figure 14. The pivoting frame places the wall components in a horizontal position. This is necessary for cutting in a efficient way.
Recycling Prefabricated Building Components for Future Generations
Figure 15. The concrete is cut by a joint cutter.
193
Figure 16. After cutting, the interior walls will be set – in an upright position, as during transportation.
11 REASSEMBLY The construction grid of the prototype must reflect the actual specification. This is advisable to minimize the treatment of components. But in principle all linear-plan views are possible, because all components are extracted from interior walls or floor slabs by cutting a specific dimension. Cutting provides a smooth, butt-jointed wall joint, comparable to new components. The fixing points in the concrete components were largely provided with demountable heavy-weight dowels. This facilitates simplicity of adaptation during the life cycle of a building and provided optimised separation of individual materials for better recycling.
Figure 17. The bottom slab of the prototype, created from pre-stressed slab components.
Figure 19. The flat roof of pre-stressed concrete slabs. Mounting is by demountable heavyweight dowels.
Figure 18. The first wall components. The cut components are attached on the straight ends. Connection is by plug-ins and clamps.
Figure 20. The main task was to test a roof at an angle of 45 degrees. Walls and roof are also pieces of recycled components.
194
Recycling Prefabricated Building Components for Future Generations
12 CONCLUSION This research project succeeded in demonstrating that recycled concrete and pre-stressed concrete components, depending on the engineering method, can be profitably used for construction, both in economic and ecological terms. This construction method suggests an innovative application in civil engineering and offers new market opportunities. The essential prerequisite is a recognition of ‘recycled slabs’ as a construction material. Successful application of this scheme on a wide scale will depend on the various persons concerned in the construction sector. The dismantling and re-installation process not only requires logistical expertise but also has legal and financial aspects, and these must be improved. A new development of this kind needs commitment and leadership on the part of the public sector, which is now aiding both dismantling and demolition measures, different though these are. Advance support for dismantling (by way of both design and finance), for instance, could create an incentive for housing corporations to reconsider the re-utilisation of construction components and perhaps adopt it with enthusiasm.
13 REFERENCE Asam, C., Biele, H., Liebchen, J., 2005. Endbericht zum Forschungsprojekt: „Untersuchung der Wiederverwendungsmöglichkeiten von demontierten Fertigteilelementen aus Wohnungs-bautypen der ehemaligen DDR für den Einsatz im Wohnungsbau“, Fraunhofer IRB, ISBN 3-8167-6954-3
Reuse Possibilities of Dismantled Building Elements from Pre-fabricated Concrete Buildings C. Asam Institut for Preservation and Modernisation of Buildings at the Technical University of Berlin
ABSTRACT: This paper illustrates the present activities of re-use concrete components from dismantled panel buildings. Considering as examples three little houses are giving an idea how the process of re-use works. The examples are optimized at owner’s option. They are showing the architectonical and design engineering possibilities of large panel elements. 1 INTRODUCTION In comparison to normal construction methods, new construction with recycled building elements presents unique challenges with regard to procurement of the building elements, adherence to building codes, as well with respect to structural and economic considerations. The examples documented by the following pilot projects show that economic considerations play a major role in the acceptance of this building method in the marketplace. 2 PROTOTYPE: MOVING THE TEST BUILDING As described in the “general aspects”, the test building was conceived as a demountable structure from the beginning of the planning phase on. The design of the building was carried out together with the architectural firm Krüger Wiewiorra since this firm also had access to a suitable building site for the later “remounting”.
Figure 1. The test building before dismantling.
After the structural tests were finished on the test building it served as an exhibitive example for interested clients, research visitor groups, and public events of the TU (Technical University) Berlin. In November 2005, the building was dismantled in the TU experimental lab building and prepared for the move to the outdoor site. The goal pursued during this dismantling process was to check the suitability of the building components for remounting and to make sure the recycled elements were suited for reuse in a new building setting. Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved
196
Reuse Possibilities of Dismantled Building Elements from Pre-fabricated Concrete Buildings
Special consideration was given to the dismantling ease of the anchor fittings. Additionally, damage to the individual elements that occurred during the dismantling process was analyzed and registered. The building workers deployed here were already familiar with dismantling procedure and the prefab building elements. The result: almost no damage to the building elements was incurred during the dismantling process. One day was required for the entire demounting process. The knowledge gained here proved essential for future projects. Without experience in handling recycled building elements it is difficult or impossible to implement the easy reuse of building elements in building additions or alterations.
Figure 2. The test building is dismantled.
Figure 3. The anchor fittings could be disconnected without damage to the building elements.
2.1 Reinforcement of Building Elements Due to the increased structural loads of the roof construction it was necessary to reinforce one roof element in the lintel zone. To accommodate architectural considerations a ceiling-flush beam was foreseen. Before moving the element it was additionally reinforced with CFK slot plates. The CFK slot plate technology presents new potentials for building element reinforcement. Whereas the already widely used CFK strip plate technology utilizes reinforcing plates glued to the exterior surface, the CFK slot plates are recessed into slots cut into the element. This increases the load transfer capability of the glue layer markedly. Additionally, fire protection capability is also increased. And according to DIN 1405-1, the slot plate method is allowed for concrete reinforcement measures.
2.2 Remounting Remounting of the test building took two days. The tight site in a courtyard of a Berlin apartment building had to be accommodated. Normally, the remounting process could have been carried out in one day. The remounting process was carried out in the same order, as was the original building. The first step was to mount the floor slab on strip foundations laid on setting mortar.
Reuse Possibilities of Dismantled Building Elements from Pre-fabricated Concrete Buildings
197
Figure 4. Loading the dismantled wall elements in the experimental labs of the TU Berlin.
The remaining open joints were filled with rubber granulate matting. The old mats could be reused here. The same type of anchor fittings used in the original building, manufactured by Fischer Anchor Fittings, was utilized for the remounting process. Even though the old anchor fittings were easily loosened it was not possible to reuse old fittings or their drill holes. It was therefore required to drill new holes for the anchor fittings.
Figure 5. Above: The floor slab is set in mortar. Openings were foreseen in the floor slab to accommodate technical installations. Figure 6. Below: The remounting site in the courtyard of a Berlin apartment block is very tight. Nonetheless, it was possible to carry out the remounting process with negligible extra effort.
The tight site situation led to some problems while positioning the building elements but this could be corrected by implementing crowbars. Altogether it was possible to attain a high level of exact mounting precision similar to that common in new building construction.
198
Reuse Possibilities of Dismantled Building Elements from Pre-fabricated Concrete Buildings
Figure 7. The last roof plate is mounted.
Figure 8. After the mounting process the building hull was fitted out as an exhibition pavilion.
Then the client fitted out the building as an exhibition pavilion. Interior insulation was foreseen in order to retain the visible, raw pre-fab concrete exterior character. The longevity of the concrete building material was analysed in detailed studies. Carbonised strips were measured at the relevant points, non-accessible zones were foreseen with a CO2resistant layer, and accessible zones were analysed in regard to rust corrosion. Through implementation of the root/time law it was possible to calculate the carbonisation process and to determine adequate inspection intervals. The worst case scenario – wherein the building is assumed to stand as an uninhabited ruin with no renewal or repair of joint sealants for 50 years – foresees a time span of 50 years before the first structural damages to roof reinforcement steel would be encountered. As long as the building is kept dry there is no danger of structural failure of the floor slabs. It would take 475 years before corrosion from the exterior could cause significantly structural damage. Even without care and refurbishment measures there no danger to life or contents can therefore arise. The construction system utilizing recycled concrete building elements is therefore also very safe for exterior construction, and this will be additionally confirmed by future analysis and experiments. 3 FIRST PILOT HOUSE: SMALL HOUSE WITH FLAT ROOF General project information: The building is a freestanding single-family residence. The net floor plan area measures 212 square meters. The house is comprised of eight rooms, one kitchen, two bathrooms, a roof terrace, and a room for technical installations. Recycled elements were also used for the freestanding double garage. The KfW60 energy efficient house standard was implemented. This was attained through implementation of a foundation heat pump for space and water heating. Heating is distributed through a floor heating system. The building hull was foreseen with 14 cm thick floor insulation (WLG 0,040), the walls were foreseen with 15 cm thick insulation (Ȝ = 0,032 W/mK). The client opted for double glazed wood frame windows. The flat roof was executed in standard flat roof construction. The roof insulation was foreseen in 20 cm thickness. Building measures commenced in June 2005 and were complete by October 2005. Remounting 34 floor/roof slab elements and 56 wall elements took 7 workdays. 27 whole floor/roof slab elements and 22 whole wall elements from the large residential settlement Marzahn (5 km distant) were used here. The elements were thoroughly prepared for remounting on the dismantling site in Marzahn and then transported to Mehrow. The building costs for building shell construction and interior fitting work were tabulated by Conclus architects, who were responsible for the construction process, at 840 EUR per square meter.
Reuse Possibilities of Dismantled Building Elements from Pre-fabricated Concrete Buildings
199
3.1 Montage The adjacent diagram depicts the level-by-level mounting process employed here. The first diagram shows the floor slab that was also constructed in recycled building elements. The slab on the left side, where the dining room is located, was sunk to allow a barrier-free access to the roof terrace above it. The next diagrams show the walls and floor/ceiling slabs of the ground floor that were all constructed in recycled building elements. Only the stair up to the upper level (not portrayed here) was built as a newly constructed element. The upper level was also mostly constructed in recycled building elements. It was only necessary to build one light separation wall in the room above the living room because no load bearing wall was located beneath it.
Figure 9. The building phases of the Mehrow pilot house.
Figure 10. Mounting of a wall element.
The roof elements were also completely constructed in recycled building elements. The mounting process was executed by a construction firm that specialises in pre-fabricated concrete construction methods. The walls and cut floor slabs had to be foreseen with new transport anchor points to allow their transport. The uncut slabs were all transported via their original transport anchor points. The elements were connected using heavy-duty anchor connectors as specified in
200
Reuse Possibilities of Dismantled Building Elements from Pre-fabricated Concrete Buildings
the prototype. The ring beam was foreseen at ceiling level and created using flat steel profiles. The connections here were also executed with heavy-duty anchor fittings. The necessary window and door lintels were fabricated in new building elements made of steel. Building joints were filled with cement mortar. 3.2 Interior Fittings After the new lintel beams were clad the window-doors were mounted in front of the exterior wall surface. The exterior walls were foreseen with a WDVS façade system (heat insulation in connection with stucco exterior surfacing). The client required that interior walls be plastered. Electrical installations were recessed in the plaster layer. This made it necessary to implement costly measures in order to countersink vertical cables and electrical sockets into the massive pre-fab concrete elements. The horizontal electrical installations were largely integrated in the floor construction zone. The sanitary installations in both bathroom and WC were foreseen as wall-hung elements.
Figure 11. 1 rst pilot house: Street-side elevation shortly before conclusion of building measures.
Figure 12. 1 rst pilot house: Garden elevation shortly before conclusion of building measures.
4 SECOND PILOT HOUSE: SMALL HOUSE WITH PITCHED ROOF General project information: This second privately funded project built after the Mehrow house was erected in Schildow. This project is comprised of two single-family residences that are connected by a bridge structure. Additionally, garages and auxiliary buildings are also foreseen in recycled pre-fab concrete building elements. The floor area of the homes measures 186 and 101 square meters respectively. The KfW40 energy efficiency standard was specified. Building commenced in June 2005, mounting of the elements began in September 2005. 200 elements recycled from 60 whole floor/roof slabs and 50 interior wall elements comprise the main structural elements. Differences of opinion between those involved in the building process led to delays. The positive experiences gained on the first house project could only partially be continued here. To effectively utilize recycled building elements it is decisive for all of those involved in the building process to work together and cooperate fully because this building method is still experimental and cannot yet be executed in a standardised fashion. The special characteristic of this project is the implementation of pitched roofs that are built entirely of recycled building elements. Additionally, a two-story atrium space was foreseen in the larger house. Both of these details were tested beforehand in the experimental lab of the TU Berlin.
Reuse Possibilities of Dismantled Building Elements from Pre-fabricated Concrete Buildings
Figure 13. Visualisation of the south-west building sides. [Conclus]
201
Figure 14. Visualisation of the north-west building sides. [Conclus]
Figure 15. The building phases of the Schildow pilot house (main house).
The schematic system developed for this pilothouse is described in the following text. The floor slab is comprised of floor slab elements laid on strip foundations. The insulation under the floor slab was foreseen in foam glass chips, a material that is a by-product of recycled glass. The walls were set in the already-practised fashion in a mortar bed and connected with anchor fittings. The ceiling above the ground floor was left open on one corner of the house to create the two-story interior atrium space. The six by three meter large elements here were adapted accordingly. The exterior wall of the atrium space is made of adapted floor slab elements. All of the walls and floor slabs are made of recycled building elements. Only the stair is foreseen as a new prefabricated concrete element.
202
Reuse Possibilities of Dismantled Building Elements from Pre-fabricated Concrete Buildings
The pitched roof with a pitch angle of 25 degrees is also made of recycled building elements. The triangular pitch elements and the ridge beam were cut out of load-bearing interior wall elements. The triangular elements were carefully cut out of former interior wall elements to assure that reinforcing steel for transport stability was amply present in the lower third of the triangle. The roof elements were mounted on rubber strips and anchored to the triangular elements. After element mounting the roof plates were connected at the ridge with steel lashes and a ring anchor was created with new steel strips.
Figure 16. Complete shell construction.
5 CONCLUSION The pilot projects document the possibilities inherent for the use of dismantled pre-fabricated concrete building elements in contemporary housing. The pre-fabricated concrete elements supplied from dismantled buildings were of good quality. It became clear that the successful implementation of the recycling process is dependant on well-functioning logistics. This encompasses determining the availability of the elements and also planning and executing precise building execution on site. Additionally, the quality of the building elements must meet current building codes. When all of those involved in the building process cooperate well, it is possible to construct very economical and ecological buildings with this method. Since costs for transporting the elements from the spender building to the recipient building play a major role in determining the economic viability of these projects it is advantageous when the new buildings are constructed as part of the ongoing transformation and renewal of the large residential settlements or in their nearby vicinity.
Typical Measures on Load Bearing Building Elements During Modernisation C. Asam Institute for Preservation and Modernisation of Buildings at the Technical University of Berlin
ABSTRACT: This paper gives an overview about typical measures during high-class modernisation of block buildings. The focus is on the construction needs of prefabricated concrete buildings. Three main points are characterized. The first is the creation of new wall openings. The second is engaged in the area of transformation of floor/roof slab elements into roof terraces and the last one describes a possibility to create a barrier-free opening for balconies. 1 INTRODUCTION The housing surplus of over one million housing units in Eastern Germany has led to the dismantling of prefabricated concrete buildings in large residential settlements there. In this process, a large proportion of the buildings are being only partially dismantled. After the partial dismantling has been carried out the remaining building substance is often modernised and refurbished. After dismantling the building substance remains as a building shell. Depending on the standard of the original building substance some building elements can often be preserved and integrated into the refurbishment concept. This often applies to parts of the sanitary installations, parts of the heating systems or sometimes parts of the elevators. During complete refurbishment measures it is though necessary to renew technical systems, floors, doors, windows, and the exterior building surfaces. The building measures are comparable to those required during normal new building construction and will not be further considered here. Other typical measures that are executed on load-bearing elements in order to greatly improve the existing structures are discussed here. These include: Creation of new wall openings Transformation of floor slabs into roof terraces Creation of barrier-free openings 2 CREATION OF NEW WALL OPENINGS The creation of new wall openings within existing elements is necessary when new window openings or balcony accesses are required. Additionally, it is often necessary to increase interior opening sizes, for example when barrier-free access is required or when higher door openings result due to increased floor thickness. During execution of the cutting measures it is necessary to transfer loads out of the cutting zone of the element being handled. This can be achieved either by executing temporary supporting measures or by previous additional strengthening of the relevant building elements. 2.1 Temporary support measures Temporary beams and scaffolding can be mounted to redirect bearing loads in the area to be cut. The required structural dimensions depend on the loads that must be carried. A disadvantage of this solution lays in the reduction of working space by the scaffolding elements that results in limited space for execution of the sawing process. Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved
204
Typical Measures on Load Bearing Building Elements During Modernisation
If only limited space is available for the cutting apparatus, alternative supporting flange systems utilizing steel lintel beams bolted to the adjoining building elements can be employed instead of steel column supports. The steel section is secured with steel bolts above the planned opening before cutting. After securing, the steel section serves as an effective lintel. This solution has the advantage that no column takes up much needed space necessary for executing the cutting process. The cutting height is defined by the temporary lintel element. The last step is the insertion of the lintel beam. To reduce setting of the zones above the lintel high-density mortar should be used. If fire protection is required the necessary cladding must additionally be foreseen.
Figure 1. Preparation of the temporary supporting measures.
Figure 2. Situation before mounting the lintel beam.
Figure 3. Situation after insertion the lintel beam.
2.2 Without temporary support measures A further alternative to create new wall openings in existing building elements is to execute a permanent reinforcement of the new opening zone. This solution is viable when the temporary measures described above are very extensive or create barriers for the cutting process. This applies when, for instance, multi-layer construction elements have to be cut. Three-layer exterior wall elements require removal of the bearing layer before steel bolts can be secured. It is even more complicated to execute cuts in the bathroom cell zone. Here, one must cut through the bathroom cell wall, the bearing layer, the insulation, and the exterior layer. Temporary supporting measures in the load-bearing layer can only be executed after extensive demolishment of the non load-bearing layers. In this case it is advantageous to insert the load-bearing lintel element before executing the cutting measures. The example portrayed here depicts the creation of a window opening in an existing building element. Multi-layered elements require the removal of non load-bearing layers and exposure of the bearing layer. After removal of non load-bearing layers, an adequately dimensioned steel
Typical Measures on Load Bearing Building Elements During Modernisation
205
section is fastened to the wall. The connections between the concrete wall and the steel section must be dimensioned and constructed to assure an effective direct connection of the new structural elements with the existing structure.
Figure 1. Preparation of the temporary supporting measures
Figure 4. Window zone with flange-connected lintel beam.
Figure 5. Cutting out the window opening with a wall saw.
Figure 6. Window opening before mounting of the window element.
Figure 7. Completed measure, the window frame and the lintel were integrated into the facade insulation system.
The major advantage presented by this alternative is the relatively small, limited modification of the existing building substance. A disadvantage must be seen in the low bearing transfer achieved through the point-connected steel sections that therefore must be over-dimensioned in comparison to the actual bearing loads that occur. Additionally, such bolted-on systems can only be utilised when a later cladding of the entire element is possible. This is possible when three-layer elements are reinforced on the exterior side and a external thermal insulation composite system additional exterior façade cladding is foreseen. When implemented in interior surfaces the supporting elements can be clad in dry-wall construction. A reinforcing alternative is presented by the implementation of CFK-slot reinforcements. This system is discussed in the following chapter.
206
Typical Measures on Load Bearing Building Elements During Modernisation
3 TRANSFORMATION OF FLOOR/ROOF SLAB ELEMENTS INTO ROOF TERRACES Another major construction aspect in the partial dismantling of prefabricated concrete buildings is the improvement of the uppermost living levels. Hereby, two variations are currently being realised: Construction of newly built, set-back roof levels as penthouses Stepped-back building sections with new roof terraces
Both of these solutions utilise former floor slabs as terrace slabs. This requires both a new solution for the insulation as well as a structural solution that accommodates increased loads. The load increase of live loads for slabs with adequate lateral distribution previously calculated at 1,5 kN/m² must be increased to 3,5 kN/m² + 2 kN/m². Even if one deducts the factor of 0,75 kN/m² factored in for light non load-bearing walls, 1,25 kN/m² of added loads must still be accommodated. Creating terraces thus requires newly calculated and reinforced floor slab elements. This can be achieved by various measures: Slab strengthening with glued reinforcement elements Creating a continuous structural system Experimental building element certification.
The tight site situation led to some problems while positioning the building elements but this could be corrected by implementing crowbars. Altogether it was possible to attain a high level of exact mounting precision similar to that common in new building construction. 3.1 Slab strengthening with glued-on reinforcement elements Glued-on CFK strips are commonly used to reinforce floor/roof slabs. These strips are merely a few millimetres thick and are especially effective for strengthening reinforced concrete and prestressed concrete slabs. Here, when dealing with multifamily housing blocks, it is always necessary to accommodate fire protection building codes with costly cladding that generates additional expense. Additionally the installation of the glued-on strips over the entire opening length often results in additional building measures, as any walls in the way must be partially removed at the ceiling joint to accommodate the continuous reinforcing strips. To date, the glued-on strips have a major disadvantage. They can only be implemented as reinforcement for steel reinforced concrete elements. Safety specifications require a set minimum amount of reinforcing in the building element. Since some cross-spanning floor/roof slab elements do not have the necessary reinforcement required this strip reinforcement system cannot be employed here. Recently, new slot reinforcement elements have been developed that are not subject to these limitations. These new reinforcement strips are recessed into slots and hence protected on three sides by the concrete and can therefore be deployed in non-reinforced building elements. The major advantage of this more costly alternative lies in the fact that the elements are completely recessed into the building elements and are therefore flush with the element surface. The full adhesion functions similarly to steel reinforced concrete. Therefore dimensioning is calculated in reference to DIN 1045-1.
Typical Measures on Load Bearing Building Elements During Modernisation
Figure 8. The recessed adhesive CFK-slot reinforcements substitute a lintel.
207
Figure 9. The slot reinforcements are inserted into recessed slots previously filled with epoxy glue.
3.2 Creating a continuous structural system Creating a continuous structural system can be implemented when several floor/roof slab sections (at least two sections) are foreseen on one level. Since the slab elements were calculated and built as single field systems that are interconnected to the neighbouring slabs merely by point-loaded tension connections it is possible to increase their load-bearing capacity by creating stiff connections between the slab elements. This experimental concept could be calculated, proven and built on a rooftop design of a partially dismantled prefabricated concrete building that was architecturally improved with a new stepped-back penthouse level.
Figure 10. Anchor connections were created before a 6 cm concrete layer was laid.
Figure 11. Plan of the anchor location.
Figure 12. Plan and section of the roof level of the existing building.
208
Typical Measures on Load Bearing Building Elements During Modernisation
Figure 13. An experimental calculation process made it possible to certify that the required load-bearing capacity was met. The diagram depicts the creation of a continuous structural system.
Since this reinforcement alternative method is executed on the upper slab surface above the slab bearing supports all cross walls in this zone must be dismantled. Then an adequately dimensioned layer of concrete is foreseen to the left and right of the bearing supports and connected to the existing slabs to create a stiff connection. This stiff connection between the existing building element and the new concrete allows this reinforcement solution to function successfully. It is usually necessary to additionally foresee an anchor connection to create a structurally effective permanent bond. Since the described projects are large-scale the expenditures for anchor connections play a major role in the cost effectiveness of this solution. At the present stage, no industry-proven, cost effective systems are available. 3.3 Experimental building element certification In conclusion, a final possibility that requires no building measures should be mentioned: the long-practiced method of recalculating the structural loads with an alternative concept for calculating structural loads. DIN 1405-1 foresees experimental building element certification as an alternative to the normal calculation process. This method involves actual simulation of the required loads. If these are met and the building element displays lower deformation levels than required, the building element is then certified as capable of supporting the defined loads.
Figure 14. The residential quarter before refurbishment measures were executed.
Figure 15. The residential quarter after refurbishment. Roof terraces were erected in the partially dismantled prefabricated concrete buildings.
Typical Measures on Load Bearing Building Elements During Modernisation
209
A statistically determined number of tests of a given element type allows the certification of the load-bearing capacity of the untested elements even though testing of but a small number of actual elements is carried out. A safety factor is calculated that, together with the required loadbearing capacity, equals tested load-bearing capacity. This factor is dependent on the number of tested elements and on the homogeneousness of the to-be tested total of all elements. The element portrayed in figure 14 and 15 met the required load-bearing strength without additional reinforcement measures. This allowed saving the expenditures for the already planned CFK reinforcement measures. Figure 16. Experimental load-bearing certification of the slabs with a hydraulic load simulator.
4 CREATION OF BARRIER-FREE OPENINGS Barrier-free entrances and openings are an increasingly important factor for the marketability of apartments, given the growing number of senior citizens in the population. For this reason, refurbishment measures of apartment circulation spaces, corridors, bathrooms, kitchens, and loggias/balconies are very often executed with barrier-free measures. Apartment refurbishment often requires widening door openings. Please consult the Chapter Creation of New Wall Openings for relevant information on this point. To create barrier-free circulation it is possible to remove web elements. This does not affect the overall structural stability of the building. The dismantling and transport capacity of the exterior wall elements themselves is though adversely affected when webs are removed. If these elements are to be later dismantled or transported they must then be additionally reinforced.
Figure 17. Barrier-free loggia entrance as depicted in figure 18.
210
Typical Measures on Load Bearing Building Elements During Modernisation
Figure 18. Detail of the original loggia entrance.
Figure 19. Detail of a barrier-free solution for a loggia entrance.
5 CONCLUSION These examples illustrate the fact that a large number of contemporary strategies can be implemented to transform prefabricated concrete residential buildings. The described examples often meet with criticism from a financial standpoint. Nonetheless, even cost-intensive measures such as CFK glue-on reinforcements, concrete sawing, and experimental certification of existing load-bearing capacities can be more cost effective than comparative new building measures – given a well-prepared and thoughtful preliminary planning phase.
Safety Evaluation of External Sandwich Panels in Large-panel Buildings A. Kozáowski, A. Rybka & Z. Plewako Rzeszów University of Technology, Poland
ABSTRACT: In multi-storey large panel dwelling buildings, external walls were constructed from three layers: façade layer made from reinforced concrete, thermal insulation layer made from polystyrene or mineral wool and structural layer made from reinforced concrete. Connection between these three layers consisted of fasteners and pins made of steel bars. From the safety point of view, the most important structural elements in sandwich panels are steel hangers. The main defects observed in the external panels of existing buildings have been described as well as methods of improving the safety of connections between layers. 1 GENERAL DESCRIPTION OF THE PROBLEM Most of the dwelling buildings erected in Poland in 60-80 were done in large-panel technology. This was dictated by great demand for new flats caused by lack of flats, quick industrialization and high increase in population in those years. In 1990s high cost of large panel buildings forced changing technology to traditional one, with the use of some prefabricated elements like hollow floor slabs and stairs. Nowadays flats in large panel buildings amount ca 30 % of global number of flats (Plewako et al. 2004). In Poland there is still lack of around 1,2 mln flats, but the main concern is maintenance of large panel buildings in good condition, liquidation of observed faults and improvement, mainly thermal insulation connected with exploitation costs. From the structural point of view the most dangerous are cracks in external panels and their joints as well as corrosion and fatigue of hangers connecting external layer to structural one. Few cases of falling down external layer of sandwich panels were observed in last decade. The main problem of current maintenance of large panel buildings is evaluation of safety of external sandwich panels in such buildings and application of the appropriate strengthening methods. 2 PROBLEM CONCERNING STRUCTURE 2.1 Typology of the structures In multi-storey large panel dwelling buildings, external walls were constructed from three layers (Fig. 1): - façade layer made from reinforced concrete -1, - thermal insulation layer made from polystyrene or mineral wool -2, - structural layer made from reinforced concrete -3.
Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved
212
Safety Evaluation of External Sandwich Panels in Large-panel Buildings
Figure 1. Typical sandwich large panel (Woyzbun & Wójtowicz 2002).
Structural layer of walls is made from concrete of thickness 8 to 15 cm, depending on whether the wall is only a curtain or load bearing. This layer works in rather good condition, it is not subjected to atmospheric action – its durability can be assumed for 100 years. Façade layer, also made from concrete of thickness 5-6 cm is reinforced by steel net made from bars diameter 34,5 mm, spaced 20x20 cm. The main role of this layer is to protect insulation layer against atmospheric actions and mechanical damages, and also to protect steel hangers against corrosion. Thickness of thermal insulation was initially 5 to 6 cm, than after 1982 was increased to 8-10 cm. Connection between these three layers consisted of fasteners (4), and pins (5) made of steel bars (Fig. 1). Typical cross section of external wall applied in OWT system is shown in Fig. 2.
Figure 2. External wall in OWT structural system (ĝciĞlewski 1998): 1 – structural layer, 2 – thermal insulation, 3 – façade layer, 4 – hanger.
Two kind of fasteners were used: - hangers (Fig. 3), made of steel bars 8 mm, which carry loading coming form weight of façade layer, but must be enough flexible to allow thermal movement of façade layer. These hangers are of triangle shape and are anchored in façade layer by one or two anchorage bars ĭ 8 of length 300 mm. Cover of hangers should be min. 15 mm. Two types of hangers were applied, depending on the way in which sandwich panel was concreting (see Fig. 3a and 3b). - pins (Fig. 4), made of steel bars 3-4,5 mm, which were placed around plate perimeter and around openings for windows and doors. They are designed to carry wind sucking and to stabilize thermal insulation.
Safety Evaluation of External Sandwich Panels in Large-panel Buildings
213
anchoring rebars 8mm l = 30 cm
anchoring rebars 8mm l = 30 cm
Figure 3. Anchorage of hanger in façade layer (ITB 1999, Woyzbun & Wójtowicz 2002): a) concreting with façade layer in the bottom; b) concreting with façade layer on the top; 1 – façade layer, 2 – thermal insulation, 3 – structural layer, 4 – reinforcement net, 5 – anchorage bar I 8, l = 300 mm.
Figure 4. Anchorage of pins (ĝciĞlewski 1998); 1 – pin, 3 - reinforcement net, 5 - structural layer.
From the safety point of view, the most important structural elements in sandwich panels are steel hangers. Their destruction can lead to falling down of façade layer, which mass is about 1-2,5 tons. Arrangement of hangers in typical structural systems are presented in Fig. 5 to 7.
214
Safety Evaluation of External Sandwich Panels in Large-panel Buildings
Figure 5. Curtain walls in W-70 and Wk-70 systems (Woyzbun & Wójtowicz 2002).
Figure 6. Structural walls in OWT system (Woyzbun & Wójtowicz 2002).
Figure 7. Structural walls in W-70 and Wk-70 systems (Woyzbun & Wójtowicz 2002).
Safety Evaluation of External Sandwich Panels in Large-panel Buildings
215
2.2 Problems Hangers are working in very danger environment, they are subjected to: - high lever of stresses, - corrosion, in case of water penetration into thermal insulation - hangers are not covered by concrete, - fatigue from thermal movement of façade layer. The main faults, stated by Building Research Institute, Warsaw (ITB 1999), are as follows: - bigger then designed thickness of concrete in façade layer. This thickness was bigger of 15% to 65%, what increase stresses in the hangers, - smaller thickness of thermal insulation, specially made from mineral wool. Average observed thickness of this layer was 38 mm, in comparison to the design value of 60 mm. This leads to increasing effects of thermal movement of external layer, - incorrect anchorage and cover of hangers stated in more than 50 % of investigated cases, - cracking of external, façade layer, which can lead to leakage of rain water into insulation layer and increase the danger of corrosion. 2.3 Current technical state of sandwich panels Current condition of large-panel buildings facades is not satisfactory (Kozlowski et al. 2004). The reasons for this are: mistakes and faults during designing, production and transportation of large panels, assembly mistakes and lack of current conservation and reparation. The main indicator of safety of hangers is steel grade used to produce them. The requirements for steel grade for hangers are presented in Table 1.
Table 1. Requirements for steel hangers grade. Period of time till 1973 1973 - 1982 after 1982
Structural systems W-70 Wk-70 not specified H13N4G9 OH17T H13N4G9 St3SCuX with OH17T zinc coating H13N4G9, 1H17N4G9, 0H17N4G8, 0H18N9 plain carbon steel with zinc or aluminum coating
OWT St0, St3Cu H13N4G9 St3SCu St0, St3SX with zinc coating
Szczecin
H13N4G9
Requirement for steel: minimum fu 380 MPa, minimum fy 240 MPa, elongation in failure: A5 minimum 30 %, bending on bar 2 d: 180o without cracking.
Building Research Institute had conducted for twenty years wide investigation on large panel building (Konieczny 2002). More then 800 panels were investigated, amongst them 512 hangers. Because of safety of existing buildings, only 27 samples of hangers were taken and used to recognize steel grade. Results of these tests are presented in Table 2. 21 tested hangers were made of 11 different steel grades. Plain carbon steels (St0 and St3 groups) were mainly used. Steel grade St3SX and St3SY were applied in 1970s years when no special requirements had been established, or these steels were used in case of lack of stainless steel. In OWT system steels St0 and St3SCu were accepted. During design study phase environmental conditions were considered as high corrosive to steel. Durability of these hangers was assumed as 20 to 40 years.
216
Safety Evaluation of External Sandwich Panels in Large-panel Buildings
Table 2. Results of steel grade tests. Steel grade St0 St3SX, St3SY St3SX + zinc coating 1H13 2H13 H17 2H17 H17T OH17T OH13 H13N4G7 Total Non-magnetic steel (unknown grade) TOTAL
Number of objects 1 6 1 1 1 1 1 3 3 1 2 21 6 27
Current investigation showed that real environmental conditions were not so aggressive. Insulation layer materials were dry (1.5% to 2% of RH). From all investigated buildings only in 3 cases surface stain was observed and in one local pitting corrosion to 0.2 mm deep occurred (after 8 years of service). Generally, for these steels there was no safety reduction due to hangers corrosion. Chrome steel grade OH17T was accepted for W-70 and Wk-70 systems. Another chrome steel grades were applied in case of lack of appropriate ones and their declared stainless was decisive. But for these steels danger lays in much smaller ultimate elongation necessary in the process of hangers forming and fatigue loads. Tests made in objects after 12 to 14 years of service showed cracking of hangers in bent places. The cracks were perpendicular to bar diameter and went through whole cross-section. It was concluded that the crack occurred during exploitation, because cracked hangers could not be installed. Cracks resulted from inter-crystal stress corrosion. Based on micro-structural steel tests following cracks causes were stated: - improper steel structure; bars were produced omitting heat-treatment process, - faults in panel forming that caused lack of proper concrete cover, subjecting the hangers to environmental influence (moisture), - stress action produced by hangers forming and service conditions. Cracks in hangers decrease safety to dangerous level and may cause falling off façade layers. Assessment of the actual condition of panels shall be based on the analysis of all examined parts of panel. In all cases where significant differences between requirements and real technical condition occurred, intervention is recommended. Typical faults that could appear in existing panels and suggested recommendations are presented in Table 3. 2.4 Actions The following actions should be considered during evaluation of safety of sandwich, external panels: - self-weight, - temperature changes, - wind sucking.
Safety Evaluation of External Sandwich Panels in Large-panel Buildings
217
Table 3. Evaluation of technical state of wall panels according to appeared faults.
Hangers anchoring in façade layer
Hangers
Insulating Façade layer layer reinforcement
Façade layer
Part
Confirmed faults - cracks in concrete > 0.3 mm - thickness of concrete > 1.1unominal - depth of concrete pH neutralization equal to rebars cover - soaking of concrete > 5% - concrete polluted by aggressive compounds - diameter and distance discordant to project - insufficient amount or lack of concrete cover - confirmed rebars corrosion and cover falling - moisture higher than acceptable - thickness < 0.9unominal
- lack of hangers - decreased number of hangers (in relation to project) - steel grade - steel corrosion - shape and diameter - hanger’s position - cracks in steel - pitting corrosion - anchoring bar diameter < 8mm - bar length < 300mm - improper bar position to hanger (for example: bar not interlaced with hanger) - lack of anchoring rebars - appeared rebars corrosion and cover falling
Recommendations - sealing the cracks or putting a new plaster - strengthening or bearing capacity evaluation of hangers - strengthening and application of surface protection - application of surface protection - individual analysis of hazards - static analysis and strengthening (if necessary) - strengthening of panels or decision of dissembling - as above - repair of panel joints sealing - bearing capacity evaluation of hangers according to heat/moisture calculations
- strengthening by additional anchors - as above - strengthening if steel discordant to requirements - strengthening of panels - supplementary anchors or strengthening - if discordant to project verifying of bearing capacity or strengthening - strengthening of panels - as above - bearing capacity analysis or strengthening of panels - as above - strengthening of panels - as above - cover repair or strengthening of panels
2.5 Description of works The best way to improve the technical state and safety of hangers and more generally external panels is additional anchorage of façade layer connected with thermal renovation of walls (adding new thermal layer). Profits from adding new, external layer of insulation are as follows: - decreasing of heat loose and cost of heating (economic aspect), - protection of water penetration through panel connections and façade layer cracks, - elimination of water condensation on hangers, - elimination of thermal movement of external layer of panels. From the structural point of view the most important for increasing safety of hangers are three last aspects. In addition, when the technical state of hangers is not satisfactory and to carry additional loading from the new thermal insulation, additional anchorage of façade layer is applied. Figures 8 to 11 present various types of applied additional hangers, usually made of stainless steel grade A4.
218
Safety Evaluation of External Sandwich Panels in Large-panel Buildings
expansion anchor façade layer
steel support structural layer
insulating layer
Figure 8. Additional connection with steel support (Konieczny 2002).
Bearing capacity of presented above support unit includes the range from 9.5 to 12.0 kN. Its height vary from 210 to 280 mm and support is fixed to structural layer by expansion anchor 12 mm. These kind of connectors are rather expensive and labour consuming. The simplest types of additional connectors with steel rods 22 to 35 mm fitted in the structural layer are presented below (Fig. 9). Bearing capacity vary from 6.5 to 12.0 kN of vertical force.
structural layer
steel anchor insulating layer façade layer
resin adhesive
Figure 9. Additional connection with steel anchors (Konieczny 2002): a) connector with “dry” steel bar assembling in fit hole b) connector with adhesive anchor.
Another type is 16 mm expansion anchor 20 mm and length 200 mm (Fig. 10)
Safety Evaluation of External Sandwich Panels in Large-panel Buildings insulating layer structural layer
219
façade layer àSR expansion anchor
Figure 10. Additional connection with expansion anchors àSR type (Konieczny 2002). insulating layer
tendon distance sleeve
expansion connector
façade layer structural layer
insulating layer
resin cement additional expansion element
expansion connector tendon
Figure 11. Connectors with steel tendons (Konieczny 2002): a) skew tendon; b) horizontal tendon.
Bearing element in solution presented in Figure 11 is steel tendon with clamped and threaded sleeves. Skew tendon carry mass of façade and tension (wind) forces; the horizontal one is taking only horizontal tension up to 4.0 kN. All presented solution of additional connectors have to fulfil requirements given in European Recommendation for Technical Approvals including: - minimum diameter of cylindrical part of connectors shall be not less than 6 mm, - minimum anchoring depth hef in structural layer made from C25 concrete shall be at least 40 mm, - minimum thickness of part where the rods are anchored hn, must be not less than hn t 2hef and hn t 100 mm.
220
Safety Evaluation of External Sandwich Panels in Large-panel Buildings
3 CONCLUSIONS Based on the wide investigation done by Building Research Institute, the following conclusions can be drawn: - during design of sandwich external panels, it was assumed that hangers would work in very aggressive, humid and corrosive condition, so their durability was estimated on 20 to 40 years. Conducted investigations shown that even in winter season moisture of mineral wool was not bigger than 2 %, so corrosion speed is very low and in most cases not dangerous, so durability of hangers is now estimated on 60 years, - inter-crystal stress corrosion was stated only in these cases where chrome steel grade H13N4G9 was applied, - in 85% of investigated buildings, the quality of concrete in external layer was good and in accordance with design assumption, - requirement of mini 15 mm thickness of the concrete cover was fulfilled only in 40 % of panels. In the places where cover was smaller that 5 mm, cracks on the surface of panels were observed along reinforcement bars. Other crack, caused by thermal stresses, did not exceed 0,3 mm, - in 10 % of tested façades improper anchorage of reinforcement net and hangers was discovered, - in most of the tested cases, there was observed increase in hangers loading caused by bigger than designed thickness of facade layer. Average increase in thickness was 15 %, but in few cases even 60 %. In any cases, when neither the technical state of hangers is satisfactory nor it fulfils requirements to carry additional loading from the new thermal insulation, additional anchorage of façade layer is applied. REFERENCES ITB Instruction No 360/99. Investigation and evaluation of concrete multi-layer panels in existing residential buildings. ITB (Building Research Institute), Warszawa 1999, (in Polish). Konieczny K. 2002. Additional connections of facade to structural layer of large external panels. ITB Warszawa 2002, (in Polish). ITB Recommendation No 374/2002 Kozáowski A., Plewako Z., Rybka A. 2004. Technical state of the envelopes in industrially constructed residential building in Poland. COST C16 WG3 meeting, Berlin, May 2004. Plewako Z., Kozáowski A., Rybka A. 2004. State of the art of current non-traditional dwelling buildings in Poland. COST C16 WG1 meeting, Berlin, May 2004, ĝciĞlewski Z. 1998. Reliability of connectors in multi-layer panels in large-panel buildings and strengthening methods. WPPK UstroĔ’98 Pĝ Gliwice 1998. (in Polish). ĝciĞlewski Z. 2004. Reliability of Large-panel Elements. Building Materials (in Polish). No 11’2004. Woyzbun I., Wójtowicz M. 2002. Methodology of technical condition evaluation of large multi-layer external panels. (in Polish). ITB Recommendation No 374/2002.
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes Jana Šelih Faculty of Civil and Geodetic Engineering, University of Ljubljana, Ljubljana, Slovenia
Blaž Dolinšek Building and Civil Engineering Institute ZRMK, Ljubljana, Slovenia
Roko Žarniü Faculty of Civil and Geodetic Engineering, University of Ljubljana, Ljubljana, Slovenia
ABSTRACT: Structural refurbishment of a multi-apartment building in Bovec, Slovenia, that suffered serious damages during earthquake in 2004 is presented. The planned program encompasses upgrading of structural, thermal efficiency and functional performance. Special attention is oriented to the earthquake resistance of the building after the refurbishment.
1 GENERAL DESCRIPTION OF THE CASE STUDY The case under consideration is located in North-West region of Slovenia in Bovec. A small neighborhood of multi-apartment residential buildings named “Brdo” was built around 1970. (Fig. 1). The building’s architecture follows the local traditional style. Each building has 12 apartments.
Figure 1. Case under consideration, Bovec – neighborhood “Brdo”
The town of Bovec is located in one of the most earthquake risk prone areas of Slovenia (Fig. 2) that was severely hit by the earthquake over the past 10 years twice, in 1998 and 2004. The refurbishment project of the building under consideration, as well as refurbishment of several other buildings, was therefore carried out within a large scale earthquake damage mitigation program initiated and sponsored by the Slovenian Ministry of Environment and Space. A large number of buildings were severely damaged during the earthquake. A methodology to determine the priority of refurbishment and to support the decision maker in the decision between refurbishment of existing building and demolition and construction of new building was prepared due to the size of damage. Improving the Quality of Existing Urban Building Envelopes - Structures. R. di Giulio, Z. Bozinovski, L.G.W. Verhoef (eds.) IOS Press, 2007. © 2007 IOS Press and the Authors. All rights reserved
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
222
During recent years, several legislation changes took place in Slovenia as a requirement to enter the European Community; structural and heat consumption / thermal insulation requirements were changed over the past 2 years. Further, the new law addressing construction demands that a building permit is to be obtained for each refurbishment project if actions interfering with the load bearing structure are foreseen. The building permit needs to be in accordance with all currently valid legislation, and therefore all essential requirements need to be fulfilled (CPD, 1987). This means that the building and its envelope need to be upgraded both from structural as well as energy efficiency point of view. The refurbishment of the building is planned to start in October 2006.
BOVEC
Figure 2: The map of Slovenia with design ground acceleration intensity for the 475 years return period
2 PROBLEMS CONCERNING STRUCTURE 2.1 Typology of structures The building has partially embedded basement, ground floor, one floor and the attic apartment. The layout is oriented along the East-West axis and is of changing shape. The length and the width of the building are 25 and 12 m, respectively. The structure has strip reinforced concrete foundations. The masonry walls are made of hollow concrete blocks laid in weak lime mortar and reinforced with vertical ties. There are no horizontal ties or they are un-reinforced. The spatial distribution of load bearing walls ensures relatively high earthquake resistance, however it is decreased due to large window openings in the exterior longitudinal walls. Floor slabs are made of cast-in-situ reinforced concrete. The roof structure is wooden and covered with fiber-reinforced cement roofing tiles. The bearing walls are 24 cm thick. The measured compressive strength of the concrete blocks is 14.1 MPa. The floor structures are 14 cm thick reinforced concrete plates made of good quality concrete. 2.2 Problems The first earthquake in 1998 caused only minor damage to the building under consideration; therefore no refurbishment was carried out at that time. Structural problems of the building stem predominantly from the 2004 earthquake action which resulted in additional severe structural damages. An assessment of the building was carried out immediately after that earthquake. A large number of wide structural cracks were identified during damage mapping (Fig. 3). The cracks follow the interfaces of elements made of different materials (Fig. 4), or they are diagonal caused by shear forces (Fig. 5). A register of all damages was compiled, and testing required to determine the mechanical properties of the bearing elements was carried out. The results of
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
223
testing and the seismic analysis of the existing building showed that the earthquake resistance was insufficient in the longitudinal direction of building. The major problems were related to the weak concrete cast in the foundations and several damages on the bearing structure and façade. Un-reinforced horizontal concrete ties were found adjacent to the stairway. Although the foundations were clearly a weak point of the structure, no differential settlements were registered.
Figure 3. Damage identification: crack mapping in the critical, longitudinal axes of building
Figure 4. Cracks appearing on the elements/ materials interface
Figure 5. Characteristic earthquake-induced shear cracks in masonry clearly visible on the render
2.3 Strategy for improvements The main problem of the building under consideration is inadequate structural performance. As already discussed, according to Slovenian legislation, the structural intervention needs to be accompanied by actions aimed at meeting all six essential requirements of CDP. The planned actions are therefore aimed at improving structural, energy and functional performance of the building. Layout changes are not foreseen. 2.4 Required actions and their implementation The performance of the building will be improved by several actions. First, the foundations will be extended by additional side concrete ties and additional layer of concrete will be added along the perimeter of foundations (Fig.8). It is vital to ensure the interconnectivity of the new foundation beams. The foundations will be adequately insulated and water drainage will be provided to ensure long term durability of the foundation structure. The cracks identified in damage mapping will be filled by injection grout. The bearing walls will be reinforced by reinforced concrete render on both sides of each wall. The render layer is 5
224
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
cm thick and covers the full length of each wall. Both layers are interconnected by anchors through the wall. In vertical direction, the mortar/renders will be anchored and interconnected through the floor slab. Energy performance will be improved by stripping off the external brick layer made of insulating non-bearing hollow clay bricks and installing adequate thermal insulation. This action will ensure that current heat consumption requirements are met. Both visual and energy performance will be improved by replacing the existing window shelves by wider elements. Due to the extent of the work carried out on the structure, the interior and exterior floors as well as the plasters will be repaired and improved. Functional performance of the overall building will be also improved due to the actions related to the electrical and mechanical installations. The roofing structure will be additionally reinforced and anchored to the bearing structure, and the roofing tiles will be replaced. The damaged chimneys will be repaired.
anchor concrete slab 14 cm steel mesh fabric 1.96 cm2/m2 concrete block 24 cm
Figure 6. Planned demolition actions (removal of all plaster layers indicated with red dotted lines)
steel mesh tie cement render 5 cm
anchors
existing foundation
added foundation
Figure 7. Designed structural intervention (ground floor); new reinforced renders are indicated in red
Figure 8. Structural intervention as designed – section A-A (foundation and exterior bearing wall)
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
225
2.5 The critical evaluation of structural intervention 2.5.1 Applied evaluation method The major dilemma is how strictly the existing buildings should be treated in the process of rehabilitation. The fact is that older masonry and reinforced-concrete structures were not constructed according to the contemporary seismic codes. The strict respect for the existing codes increases the investments in the rehabilitation. The main requirements of Eurocode 8 are to preserve human lives, to reduce economic impacts and to ensure the post-earthquake safety of important public buildings. However, these aims can be in practice achieved with certain limitations. According to Eurocode 8, the structure should be designed and constructed in the way to prevent its collapse and ensure the required post-earthquake residual resistance. Additionally, the extension of damages should be within certain limits that are defined with post-earthquake use of building and with the reasonable cost of repair works in comparison to the value of entire structure. These requirements should be also followed in the cases of post earthquake rehabilitation of damaged buildings. The approach that follows the above mentioned requirements is known as “performance based design”. It is very suitable for application in the cases of refurbishment of earthquake endangered masonry buildings. It is referred in Eurocode 8-1-4 [1] (paragraphs 3.5.3 and K.2.4 (3)) as an approximate static non-linear method. The same approach is in use in Slovenian construction and building renovation practice for the last twenty-five years. The approach has been developed combining theoretical, analytical and experimental research with on-site experiences obtained from earthquakes at Friuli (1976), Montenegro (1969), Posocje (1998) and several others. The original method became known after Friuli earthquake (1967) as “the POR method”. Story resistance envelope that determines the relationship between relative story drift and base shear resistance is obtained as superposition of resistance of all walls of story. Assuming the boundary restraints and relevant mechanisms i.e. cantilever walls, fixed-ended piers, piers coupled with spandrels, walls strengthened by reinforced plaster coatings etc., the resistance of each wall in the story can be calculated. It is usually expressed in form of bi-linear or tri-linear deformationstrength relationship representing the resistance envelope of each contributing wall. The relationship is obtained by relevant equations for the shear and flexural resistance where five basic mechanical properties of masonry are used: compressive strength, tensile strength, modulus of elasticity, shear modulus and ductility. The story resistance envelope is calculated by stepwise drifting of story for small values. The masonry walls are deformed equally and internal forces are induced according to assumed shape of resistance envelope of each particular wall. When torsion effects are induced due to displacing of the story mass center relatively to the stiffness center, the displacements of individual walls are modified. The calculation is repeated step-bystep, the particular walls are reaching different levels of deformations, and corresponding loading passing from elastic to inelastic range up to collapse state after assumed ductility is reached. When the first wall of story enters inelastic range the structural system of story and its stiffness matrix is modified. From this point forward it repeats constantly from stet to step of calculation whenever next wall reaches the elastic or ultimate limit state. The result of calculation is expressed in term of the story resistance envelope. In the each step of calculation, the level of reached ductility of walls can be presented in graphic way to get better insight in distribution of damages of walls. The several basic assumptions are taken into account when above described calculation method is used. The first basic assumption is the rigid diaphragm action of floors so that story displacements can be evenly distributed to all load-bearing walls in proportion to their stiffness. The next assumption is predominant first vibration mode shape with inverse triangular distribution of displacements over the entire height of building. The third basic assumption is that the contribution of each wall to story resistance depends on displacement imposed to this wall and its mechanical properties determined by resistance envelope. Although a wall fails in shear, it is still capable to carry its share of gravity load acting on story. The fourth assumption is the sepa-
226
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
rate action of walls although they are connected along the height with perpendicularly positioned walls. The codes require verification of structural system endangered by earthquake regarding its strength and ductility. Both are related with capacity of structure to dissipate the seismic energy and to withstand the base non-linear deformations without losing its stability. In the verification of seismic resistance the design resistance of building (SRCd) is compared with the design base shear coefficient (BSCd): SRCd t BSCd
(1)
If it is fulfilled the global ductility requirement should also be verified. The global ductility of building can be defined as ratio between the ultimate story drift and drift at the elastic limit. Considering the definition of structural behavior factor q and values given in Eurocode 8, the simple formula for deriving of the global ductility factor can be used: Pu = 0.5 (q2 + 1)
(2)
In the case of un-reinforced masonry, structures the values of q and Pu are 1.5 and 1.6, respectively while in the case of reinforced masonry structures the values of q and Pu are 2.5 and 3.6, respectively. The seismic resistance of building is sufficient according to Eurocode 8 if both criteria (Equations 1 and 2) are fulfilled. If the second criteria is not fulfilled the design resistance of building should be lowered until the ductility criteria is fulfilled. Seismic analysis was carried out for the building under consideration by using SREMB software that is based on the above described approach. The software enables seismic analysis for masonry structures and follows the Eurocode 8 (EN 1998, Design of structures for earthquake resistance) and Eurocode 6 (EN 1996, Design of masonry structures). 2.5.2 Results of evaluation of earthquake resistance of original and strengthened building The results of analysis of building in existing configuration and building with coated walls are presented in Figs 9, 10, 11 and 12. The story diagrams and diagrams showing the variations of story eccentricity were calculated for the two perpendicular directions of seismic action for all stories of original configuration of building as its strengthened configuration. In figures below are presented only responses of most critical case – ground floor of building in the longitudinal (x) direction. The actual damages of walls were not taken into account what means that the resistance of building after earthquake is substantially lower than one calculated for building as constructed. The comparison of supplied design resistance of building (SRCd) and demanded design base shear coefficient (BSCd) is shown in Table 1. The seismic resistance of original building (Table 1) was much lower in longitudinal than in transversal direction what actually resulted in damages due to earthquake action concentrated in longitudinal basement and ground floor walls (Fig. 3).
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
227
etazna sila [MN]
2 W= 7.160 MN Hid= 1.28 MN de= 1.21 mm du= 3.10 mm SRC= 0.18 duct= 2.56
meja nosilnosti Het= 1.40 MN det= 2.85 mm eet= 0.40 m
1.5
meja elasticnosti Het= 0.66 MN det= 0.63 mm eet= 1.21 m
1
meja porusitve Het= 1.01 MN det= 3.15 mm eet= 0.47 m
0.5
0
konec racuna Het= 0.29 MN det= 4.02 mm eet= 0.87 m >porusitev 60% zidov
0
0.5
1
1.5
2 2.5 etazni pomik [mm]
3
3.5
4
4.5
0
0.5
1
1.5
2 2.5 etazni pomik [mm]
3
3.5
4
4.5
ekscentricnost [m]
1.5
1
0.5
0
Figure 9. Lateral base shear force as a function of lateral displacement of the ground floor of building as has been constructed 12 0.9 10 0.8 8 0.7
y
6 0.6
M S 4
0.5
2 0.4
0
-2
0
5
10
15
20
x
Figure 10. The level of wall ductility achieved at attained story strength of the ground floor of building as has been constructed – encircled are the walls which load bearing capacity expired.
The strengthened walls influenced increase of structural stiffness and strength as well as its ductility (Table 2 and 3). At each level of base-shear attained during computational simulation the particular wall is differently deformed. The level of deformations can be related to the deformation at the elastic limit state. When this ratio is equal or higher than ductility factor of wall it is assumed, that the wall has no more shear resistance but is still able to carry the gravity load. The assumed ductility factor of un-reinforced walls is 1.5 while the ductility factor of coated walls is 4. The graphic presentation of the relative level of wall deformation and their distribution in the plan of building is very useful tool for designing of strengthening of building by adding new walls or strengthening the existing ones. This visual approach is illustrated in Figures 11 and 12 where are shown the deformation levels of particular walls attained at highest level of story base shear obtained by analysis of existing building in x-direction. It is clearly seen that the critical walls are distributed along the perimeter and in the corners of building.
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
228
p
3 meja nosilnosti Het= 2.89 MN det= 0.39 mm eet= 0.45 m 2.5
meja porusitve Het= 2.27 MN det= 0.60 mm eet= -0.67 m
2 etazna sila [MN]
j
W= 7.160 MN Hid= 2.65 MN de= 0.23 mm du= 0.59 mm SRC= 0.37 duct= 2.55
1.5 meja elasticnosti Het= 1.18 MN det= 0.10 mm eet= 0.55 m
1
konec racuna Het= 0.32 MN det= 3.87 mm eet= 1.25 m >porusitev 60% zidov
0.5
0
0
0.5
1
1.5
2 etazni pomik [mm]
2.5
3
3.5
4
0
0.5
1
1.5
2 etazni pomik [mm]
2.5
3
3.5
4
ekscentricnost [m]
2
1
0
-1
Figure 11. Lateral base shear force as a function of lateral displacement of the ground floor of strengthened building as designed
12
10
8
y
6 M S 4
2
0
-2
0
5
10
15
20
Figure 12. The level of wall ductility achieved at attained story strength of the ground floor of strengthened building as designed – encircled are walls that reached the limit of ductility capacity.
Table 1: Comparison of supplied design resistance of building (SRCd), which should be higher or equal to design base shear coefficient (BSCd) which value is our case 0.28
Basement Ground Floor
Original building Longitudinally (x) Transversally (y) 0.24 0.36 0.18 0.49
Repaired and strengthened building Longitudinally (x) Transversally (y) 0.34 0.33 0.37 0.45
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
229
Table 2: Comparison of story stiffness (MN/mm) of original and strengthened building Original building Repaired and strengthened building Longitudinally (x) Transversally (y) Longitudinal (x) Transversal (y) Basement 1.58 1.73 14.38 3.18 Ground Floor 1.05 1.66 11.80 2.50 Table 3: Comparison of story ductility of original and strengthened building
Basement Ground Floor
Original building Longitudinal (x) Transversal (y) 2.46 1.74 2.56 1.58
Repaired and strengthened building Longitudinal (x) Transversal (y) 2.96 3.55 2.55 2.96
The critical deformations were attained in weak direction of walls due to their flexural deformations. In the case of y-direction oriented walls, the shear mechanism was predominant and the level of deformations was lower than in the case of x-direction oriented walls. The visualized information on critical regions of building helps in decision making about distribution of additional walls or strengthening of existing ones. The decision cannot be made following only structural criteria but also functional criteria and other architectural demands. Therefore, several variations are usually tested and their efficiency compared before the final decision. One of the important parameters is also economic aspect of renovation. In discussed case the most acceptable solution was strengthening of certain number of walls with reinforced plaster coating. The coated walls have higher strength, stuffiness and ductility. Due to higher stiffness relatively to masonry walls, they attract higher shear of seismic forces. Therefore, they should be carefully positioned to avoid unfavorable torsion effects. As story the maximum base shear forc was acting the deformations of coated walls on their ductility limit (d/de = 4) were reached almost at all of them. 3 TECHNICAL DATA SHEET 3.1 Building as originally constructed Location of building: close to western border to Italy in town of Bovec Design ground acceleration intensity for the 475 years return period in Bovec is ag = 0.20 g Design base shear coefficient (BSCd) demanded for building under consideration is 0.28 according to Eurocode 8. Masonry building consists of: basement, ground floor, upper floor and the attic apartment. The layout 25 x 12 m is oriented along the East-West axis and is of changing shape. Foundations. strip reinforced concrete foundations. Structural system: masonry walls made of hollow concrete blocks laid in weak lime mortar and reinforced with vertical ties. There are no horizontal ties or they are unreinforced. Large window openings in the exterior longitudinal walls decrease the earthquake resistance of building Floor slabs are made of cast-in-situ reinforced concrete. The roof structure is wooden and covered with fiber-reinforced cement roofing tiles. Thickness of load-bearing walls is 24 cm: the compressive strength of concrete blocks is 14.1 MPa. The floor structures are 14 cm thick reinforced concrete After the last earthquake building suffered damages (mostly diagonal cracks) in envelope walls of basement and ground floor. 3.2 Post earthquake repair and design of strengthening Building seriously damaged during an earthquake in 2004; cracks mostly extend across the entire wall thickness of envelope walls in basement and ground floor.
230
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
Cracked mortar is removed to the depth of 5 cm on both side of the wall. Gap is filled-in with lime-cement mortar 1:1:6 and afterwards injected by using thick expanding cement paste (w/c=0.6) through the inserted steel injection nozzles. Concrete block masonry walls strengthened by 50 mm thick two-sided reinforced concrete render; concrete class C 16/20; reinforcement steel mesh fabric of 1.96 cm2/m2; Both sides of mesh anchored through the wall by 6 deformed steel anchors 8 mm / m2 Render reinforcement anchored vertically to foundation and through the concrete slabs by deformed steel anchors I10 mm/ 20 cm in length of 1m, glued with epoxy adhesive 3.3 Predicted effect of repair and strengthening Table 4. Predicted effect of reapir and strengthening of two critical stories in terms of meeting the Eurocode 8 criteria (SRCd/BSCd > 1) and increase of stiffness and ductility of critical stories.
Basement Ground Floor
SRCd/BSCd=0.28 Longitudinal Transversal 1.21 1.18 1.32 1.61
Story Stiffness Longitudinal Transversal 9.10 1.84 11.23 1.51
Story Ductility Longitudinal Transversal 1.20 2.04 1.00 1.87
The cost of the planned refurbishment is 370 EUR /m2, which makes it feasible for both founding governmental agency as well as for the residents. 4 CONCLUSIONS The extent of damage inflicted to the NW region of Slovenia dictated a rational and cost efficient way of performing the refurbishment of damaged buildings. The major problem of affected buildings is inadequate earthquake resistance which requires immediate response. The presented case is a typical representative of multi-apartment buildings from this region. The method used in the intervention, the reinforced concrete renders combined with crack sealing and reinforcement of foundations, is efficient, cost effective and easy to carry out. The total cost of the refurbishment is 370 EUR / m2, and the disturbance to the residents is minimal.
Refurbishment of Multi-storey Residential Building in Relation to the Building Envelopes
231
5 REFERENCES CPD 1998. Construction Product Directive, European Commission Technical report: Brdo 71. 2006 Eurocode 6, Design of masonry structures (EN 1996) ENV 1998-1-4 (Eurocode 8: Design provisions for earthquake resistance of structures - Part 1.4: General rules - Strengthening and repair of buildings), CEN/TC 250, Brussels, January 1996. Seismic Design Methodologies for the Next Generation of Codes, Edit P. Fajfar and H. Krawinkler, A.A.Balkema, Rotterdam, 1997. Applied Technology Council (ATC), Guidelines for Seismic Rehabilitation of Buildings Ballot Version, FEMA-273, Building Seismic Safety Council, Washington DC, USA, 1996. M. Tomazevic, Seismic Resistance verification of masonry buildings: Following the new trends, Seismic Design Methodologies for the Next Generation of Codes, Edit P. Fajfar and H. Krawinkler, A.A.Balkema, Rotterdam, 1997, p.p.323-334. Building Construction under Seismic Conditions in the Balkan Region, Volumes 3, 5 and 6, UNDP/UNIDO Project RER/79/015, Occidental Press, Vienna, 1984.
This page intentionally left blank
Conclusions Zivko Ljube Bozinovski Vice Chairman of Working Group 3A Institute of Earthquake Engineering and Engineering Seismology, University "St. Cyril and Methodius", Skopje, F.Y.R. of Macedonia
The changes from social, political, cultural, technological and economic aspect that have taken place in the countries throughout Europe have changed the requirements for design and construction of functional, humane, practical, stable, ecological and economic residential buildings. For that purpose, a continuous need is imposed for improvement of the living conditions through the improvement of the quality of buildings from the aspect of modern and functional architectural solutions, efficient, stable and economic and controlled structural systems, and use of modern materials with better mechanical characteristics, materials that are ecological and can be recycled. The problems created refer mainly to the building envelope, but in solving the structural problems related to the building envelope, structural interventions are often done also in the interior of the structure by which the behaviour of the integral system is improved. The emphasis is given on use of more sophisticated materials with better strength, stiffness and deformability characteristics, materials that are durable and resistant to external effects. The objective of each structural engineer is design of stable structures with controlled and dictated ductile behaviour of structural elements and the integral system under expected static and dynamic external effects. In the case of existing structures on which certain interventions are done, repair, reconstruction and strengthening of the structural system is carried out in order to eliminate problems incurred as a consequence of the changes of the principal structural system. In the European countries, different problems are of current concern in different countries. Common are the efforts towards finding technical solutions for overcoming of these problems and improving the structural systems. Based on the problems and the needs identified and defined in WG1 and WG2, practical solutions have been proposed for realization of the architectural requirements by which the stability of the existing buildings on which interventions are carried out is improved. Structures that were built after the fifties of the last century have been treated. In the course of time, certain damages have been manifested. These have occurred due to different reasons, most frequently ageing of materials, external effects like snow, rain, wind, frost and excessive loads as are earthquakes, land sliding, strong winds, explosives and alike. From the aspect of loads, structures loaded by vertical gravity and life loads, horizontal loads due to wind and unpredictable loads like those during earthquakes, land sliding, fires, technological disasters and mining activities, have been treated.
234
Conclusions
The main things for which the need for improvement is imposed are maintenance, partial failure and structural and non-structural interventions in the structures. Possible interventions in the structures are: adaptation of ground floors for residential premises to be turned into business premises, making openings in bearing walls, widening of openings in bearing walls, adding of balconies, galleries, extra rooms, staircases, elevators, enlargements, enlargement of attics, building of other storeys and attics, reconstructions and revitalizations. As to the typology of the structural systems, buildings of wide spectrum of structural systems and stone and solid brick masonry buildings, with and without horizontal and vertical RC belt courses, RC frame systems and prefabricated large panel RC systems of buildings have been treated. Structures damaged due to different causes as well as undamaged structures necessitating adaptation, reconstruction and revitalization have been considered. The strategy is to achieve improvement of the behaviour of the structural system through repair of damaged structures, repair and strengthening of structural elements and integral structures, strengthening of existing undamaged structures, adaptation and reconstruction for the purpose of obtaining functional space, expansion/increase of structural elements, adding of structural elements, removal or change of the principal structural system, replacement of heavy structural elements that have relatively low mechanical characteristics by lighter and better ones as well as removal of necessary dead load. Extension of balconies, enlargement and building of other storeys on existing structures is carried out for the purpose of increasing of the floor area of the relatively small flats located in the central and relatively costly locations of the large towns. To increase the standard and the functioning of the residential area, activities like making openings in bearing walls, enlargement of openings in bearing walls, incorporation of elevators, reconstruction of entrances and replacement of certain bearing elements by new ones is carried out. In most of the presented papers, certain problems have been identified and technical solutions have been proposed for overcoming of the problems. The problems and the technical solutions from some countries can successfully be applied also in other countries. From structural aspect, for each considered structure, through complex and many-faceted analysis, the main parameters of strength, rigidity and deformability are achieved such that they satisfy the requirements according to the latest knowledge on behaviour of the considered structural system under permanent, temporary and incidental loads. In the course of the duration of the COST action C16, through intensive mutual contacts, expertises, exchange of experience related to different problems regarding the improvement of the envelope of the residential structures, valuable knowledge on possible, technically consistent and efficient technical solution has been obtained. A network of experts dealing with solving of problems related to improvement of the living conditions through improvement of the building envelope has been established. The created problems have been identified, while through the presented possible solutions, the book will represent a collection of positive examples. Based on review and analysis of the presented papers, the problems treated and the technical solutions for improvement of the living conditions and generally according to the problems treated, the papers can be classified into several chapters.
Conclusions
235
Changing Image Upgrading Functionality Additions to Existing Buildings Restrengthening Recycling Improving Safety
Each chapter treats specific problems and provides examples of successful technical solutions for improvement of the building envelope. CHANGING IMAGE The urban refurbishment of the “Mireuil” District in La Rochelle can be considered as a good illustrative example of the state policy of improvement of social, architectural and environmental renovation projects of social housing. The changes of multi storey residential blocks can be in different ways to reach a new identity. That changes are necessary because insulation demands became stronger and new divisions is especially important for the owner or tenant. That is the main reason to change the identity of multi storey family blocks and at the same time to enlarge the economical life period of these types of blocks. The urban refurbishment of the district “Le Piagge” can be considered as one of the most representative interventions in terms of improvement of architectural, technological and structural performances. The problems treated are mainly associated with renovation of specific residential blocks and areas. 25% of the renovation resources account for the renovation of the envelope. UPGRADING FUNCTIONALITY A technical possibility for changing of unsuitable residential blocks made of prefabricated RC panels into modern and attractive residential compounds is presented. A flexibility is shown. An example of flexibility aimed at better utilization of space in the flats of multi-story residential buildings is presented. Part of a bearing wall is replaced by a rigid frame. A residential block has been renovated by extending flats up to an acceptable level and thus improving the living conditions. The change of architecture has also contributed to the change of the surrounding ambient. Through renovation of residential compounds, there have been created conditions for enriching contents and conditions of living whereby the settlements have become attractive for different types of users. An enlargement and building of another storey is presented through the example of a structure made of solid bricks with horizontal RC belt courses. The extension of the balconies and the building of an additional attic has contributed to functional improvements and increase of the living space. In this case, the stability of the structure under gravity and seismic loads has been checked and dictated. Namely, the dynamic response of the enlargement and the structure with the additionally built storey has been harmonized. Enlargement of balconies and building of additional balconies on buildings constructed of prefabricated RC large panel system has also been treated. The extension of balconies and building of additional balconies contributes to functional improvements and enlargement of the living space. The existing structure is relatively stable and rigid. The enlargement is flexible. It is difficult to harmonize the dynamic response of the existing and the additionally built part of a building.
236
Conclusions
ADDITIONS TO EXISTING BUILDINGS A number of examples of enlargements and additionally built storeys are presented. Another storey has been built. The living conditions have been improved and the floor area has been increased. Some latest materials with relatively better insulation properties have been used and new installations have been made, however the problems due to increase of loads and the stability of the entire structure have not been treated to a sufficient depth. Generally, problems related to reconstruction, adaptation, enlargement, building of additional storey and revitalization of existing structures have been treated. The structure has been improved from functional aspect and the living conditions have been improved. Recently developed, durable and ecologically friendly materials have been used. From the structural aspect, the concept of controlled and dictated ductile behaviour of the structural elements and the system as a whole under gravity and seismic loads expected at the site has been treated. An example of building of additional two storeys is presented. In this case, light weight materials with corresponding characteristics have been used. RESTRENGTHENING While adapting existing structures, all the structural elements that were dilapidated or expected to behave unfavourably mainly under an earthquake have been eliminated. The existing elements have been strengthened by use of materials of better strength, stiffness and deformability characteristics. RECYCLING A pilot project of reconstruction, transformation and adaptation of structures of large panel RC systems is presented. While reconstruction, it is possible to recycle the bearing panels and use them as bearing elements for construction of new structures for different purposes. The transformed structures acquire a new appearance, new functional contents and provide better living conditions. IMPROVING SAFETY The existing damaged structures are renovated based on analysis of stability, safety, durability and economy. It is generally concluded that positive examples of improvement of quality and living conditions related to collective residential buildings are presented.
COST C16 Management Committee
Belgium Prof. Andre de Naeyer Hogeschool Antwerpen Univ. College Henry vande Velde Design Sciences Mutsaardstraat 31 B-2000 Antwerp +32.3.231 6200 +32.3.231 9604
[email protected]
Cyprus Mr. Christos Efstathiades Public Works Department Republic of Cyprus Ministry of Communication & Works Lefkosia +35799597362 +35725332094
[email protected]
Cyprus Mr. George Hadjimichael Town Planning & Housing Department Demostheni Severi Avenue 1454 Nicosia +357 22 30 65 92 +357 22 30 65 01
[email protected]
Denmark Mr. Jesper Engelmark DTU - Technical University of Denmark Dept. of Civil Engineering Planning and Management of Building Processes DTU Building 118, Brovej 2800 Lyngby +45 45251932 +45 45883282
[email protected]
Denmark Prof. Ebbe Melgaard Royal Academy of Fine Arts School of Architecture Philip de Langes Allé 10 1435 København K +45 49147850 +45 32686111
[email protected]
F.Y.R. of Macedonia Prof. Kiril Gramatikov St Cyril & Methodius University Faculty of Civil Engineering Dep of Concrete and Timber Structures UL. Partizanski odredi 24 POB 560 1000 Skopje + 389 2 3116066 ext. 148 + 389 2 3117 367
[email protected]
238
COST C16 Management Committee
France Prof. Francis Allard Université de La Rochelle Pôle Sciences et Technologie LEPTAB ave Michel Crépeau F-17042 La Rochelle cedex 1 +33 546 45 82 04 +33 546 45 82 41
[email protected]
Germany Mr. Franz Georg Hofmann Federal Ministry of Transport Construction and Housing Merler Allee 11 53125 Bonn +49 228 252500 +49 228 9259 554
[email protected]
Germany Mr. Christian Wetzel CalCon Holding GmbH Management Goethestr. 74 80336 Munich +49-(0)89-552698-0 +49-(0)89-552698-75
[email protected]
Greece Prof. Charalampos Baniotopoulos ARISTOTLE UNIVERSITY OF THESSALONIKI CIVIL ENGINEERING UNIVERISTY CAMPUS GR-54124 Thessaloniki +302310995753 +302310995642
[email protected]
Hungary Dr. Tamás MezĘs University of Budapest for Technology and Economics Muegyetem rkp 3 1111 Budapest +36 1 463 2303 +36 1 463 1638
[email protected]
Hungary Prof. György Sámsondi Kiss Technical Committee Monitor Szent Istvan University Thököly Str 74 1146 Budapest +36 1 252 1270 +36 1 252 1278
[email protected]
Hungary Ms. Agnes Novak Budapest University of Technology and Economics Budapest +36 1 3060 394 +36 27 347 237
[email protected]
Italy Prof. Roberto di Giulio University of Ferrara Department of Architecture Via Quartieri 8 44100 Ferrara +39 348 3856993 +39 055 244042
[email protected]
Italy Mr. Eugenio Arbizzani Universita degli Studi di Roma "la Sapienza" Facolta di Architettura Valle Giulia Via Gramsci 53 00197 Roma +39 06 49919291 +39 06 49919290
[email protected]
Malta Dr. Vincent Buhagiar University of Malta Faculty of Architecture & Civil Engineering Environmental Design Department of Architecture & Urban Design Tal-Qroqq MSD 06 Msida +356 2340 2849 +356 21 333919
[email protected]
COST C16 Management Committee
239
Malta Mr. Ruben Paul Borg University of Malta Faculty of Architecture and Civil Engineering Mediterranea, 161, Triq Luigi Billion, Pembroke, Msida, Malta (00356)79055680 (00356)21375185
[email protected]
Netherlands Prof. Leo G.W. Verhoef (Chairman) Delft University of Technology Berlageweg 1 2628CR Delft +31.152784179 +31.152781028
[email protected]
Netherlands Mr. Frank Koopman (Technical Secretary) Delft University of Technology Faculty of Architecture (room 2.05) Chair Restoration Berlageweg 1 2628 CR Delft +31152784133 +31152781028
[email protected]
Poland Prof. Aleksander Kozlowski Rzeszow University of Technology Building Structure Civil Engineering W. Pola 2 Rzeszow Poland 35-959 Rzeszow +48 178541127 +48 178542974
[email protected]
Poland Dr. Adam Rybka Rzeszow University of Technology Faculty of Civil and Environmental Engineering Department of Town Planning and Architecture W. Pola 2 35 959 Rzeszow +48 17 8651624 +48 17 8543565
[email protected]
Portugal Prof. Luís Bragança Lopes University of Minho School of Engineering Building Physics and Construction Technology Laboratory Azurem 4800-058 Guimaraes +351253510200 +351253510217
[email protected]
Slovenia Prof. Roko Zarnic (Vice Chairman) University of Ljubljana Faculty of Civil and Geodetic Engineering Jamova c. 2 1000 Ljubljana +38641777517 +38614250681
[email protected]
Slovenia Dr. Jana Selih University of Ljubljana Faculty of Civil and Geodetic Engineering Jamova 2 1000 Ljubljana + 386 1 4768575 + 386 1 2504861
[email protected]
240
Sweden Prof. Dr. Satish Chandra Gothenburg University Institute of Conservation Box 130 St. Nygatan 23-25 40530 Gothenburg +46 31 7734709 +46 31 7734703
[email protected]
COST C16 Management Committee
United Kingdom Mr. Stephen Ledbetter University of Bath Centre for Window & Cladding Technology Bath +44 1225 826506 +44 1225 826556
[email protected]
COST C16 Working Group Members
Working Group 1 Cyprus Mr. Petros Lapithis Intercollege Art and Design Department 46 Makedonitissas Avenue Lefkosia CY, Cyprus +357 22 841 571 +357 22 353 682
[email protected]
Denmark Mr. Torben Dahl Institute of Technology School of Architecture Royal Danish Academy of Fine Arts Philip de Langes Allé 10 Dk-1435 Copenhagen K, Denmark +45 32 68 62 04
[email protected]
F.Y.R. of Macedonia Prof. Kiril Gramatikov St Cyril & Methodius University Faculty of Civil Engineering Dep of Concrete and Timber Structures UL. Partizanski odredi 24 POB 560 1000 Skopje + 389 2 3116066 ext. 148 + 389 2 3117 367
[email protected]
France Mr. Dominique Groleau Ecole Nationale Supérieure d'Architecture de nantes Laboratoire CERMA rue Massenet 44300 NANTES +33 2 40 59 21 22 +33 2 40 59 11 77
[email protected]
Germany Mr. Christian Wetzel CalCon Holding GmbH Goethestr. 74 80336 Munich +49-(0)89-552698-0 +49-(0)89-552698-75
[email protected]
Greece Prof. Ted Stathopoulos Concordia University / Aristotle University Engineering / Computer Science Centre for Building Studies Building, Civil Engineering 541 24 Thessaloniki
[email protected]
242
COST C16 Working Group Members
Hungary Dr. Tamás MezĘs University of Budapest for Technology and Economics Muegyetem rkp 3 1111 Budapest +36 1 463 2303 +36 1 463 1638
[email protected]
Italy Prof. Roberto di Giulio (Chairman) University of Ferrara Department of Architecture Via Quartieri 8 44100 Ferrara +39 348 3856993 +39 055 244042
[email protected]
Italy Ms. Silvia Brunoro University of Ferrara Faculy of Architecture via Quartieri 8 44100 Ferrara +39 347 1497462 + 39 0532 293627
[email protected]
Netherlands Ms. Marie Therese Andeweg Delft Universiry of Technology Faculty of Architecture Berlageweg 1 2628 CR Delft +31152787912
[email protected]
Poland Dr. Zbigniew Plewako Rzeszów University of Technology Faculty of Civil and Environmental Engineering Department of Building Structures ul. W. Pola 2 35-959 Rzeszów +48 602759595 +48 178542974
[email protected]
Portugal Prof. Luís Bragança Lopes University of Minho Building Physics and Construction Technology Laboratory School of Engineering Azurem 4800-058 Guimaraes +351253510200 +351253510217
[email protected]
Slovenia Dr. Marjana Sijanec Zavrl Building and Civil Engineering Institute ZRMK Dimiceva 12 1000 Ljubljana +386 1 280 8342 +386 1 280 8451
[email protected]
Sweden Prof. Dr. Satish Chandra Gothenburg University Institute of Conservation Box 130 St. Nygatan 23-25 40530 Gothenburg +46 31 7734709 +46 31 7734703
[email protected]
COST C16 Working Group Members
243
Working Group 2 Belgium Prof. André de Naeyer Hogeschool Antwerpen Mutsaardstraat, 31 2000 Antwerpen +323 231 6200 +323 231 9604
[email protected]
Cyprus Mr. George Hadjimichael Town Planning & Housing Department Demostheni Severi Avenue 1454 Nicosia +357 22 30 65 92 +357 22 30 65 01
[email protected]
Denmark Prof. Ebbe Melgaard (Chairman) Royal Academy of Fine Arts School of Architecture Philip de Langes Allé 10 1435 København K +45 49147850 +45 32686111
[email protected]
F.Y.R of Macedonia Mr. Tihomir Stojkov St Cyril & Methodius University School of Architecture Partizanka b.b. 91000 Skopje
[email protected]
France Dr. Gerard Guarracino ENTPE CNRS Department of Civil Engineering & Building Rue Audin 69518 Vaulx en Velin +33472047030 +33472047041
[email protected]
Germany Mr. Franz Georg Hofmann Federal Ministry of Transport Construction and Housing Merler Allee 11 53125 Bonn +49 228 252500 +49 228 9259 554
[email protected]
Greece Prof. Dimitrios Bikas Aristotle University of Thessaloniki (AUTh) Structural Engineering/Building Construction Dept. of Civil Engineering 541 24 Thessaloniki +(30)2310 995763 +(30)2310 420628
[email protected]
Hungary Ms. Agnes Novak Hungary University of Design and Crafts Budapest University of Technology and Economics Budapest +36 1 3060 394 +36 27 347 237
[email protected]
Italy Mr. Paolo Civiero Universiy of the Studies of Rome “La Sapienza” Dept. ITACA Via Flaminia, 70 00196 Roma +39 3286223091 +39 0644363083
[email protected]
Netherlands Mr. Frank Koopman Delft Universiry of Technology Faculty of Architecture Berlageweg 1 2628 CR Delft +31152784133 +31152781028
[email protected]
244
COST C16 Working Group Members
Poland Dr. Adam Rybka Rzeszow University of Technology Faculty of Civil and Environmental Engineering Department of Town Planning and Architecture W. Pola 2 35 959 Rzeszow Poland +48 17 8651624 +48 17 8543565
[email protected]
Portugal Prof. Manuela Almeida 23/05/2006 University of Minho School of Engineering Building Physics and Technology Group Civil Engineering Department Azurém 4800-058 Guimarães +351 253 510 200 +351 253 510 217
[email protected]
Slovenia Prof. Roko Zarnic University of Ljubljana Faculty of Civil and Geodetic Engineering Jamova c. 2 1000 Ljubljana +38641777517 +38614250681
[email protected]
Sweden Prof. Solveig Schulz Chalmers University of Technology Architectural Conservation SE-41296 Göteborg +46(31)7722441 +46(31)7722489
[email protected]
COST C16 Working Group Members
245
Working Group 3A Belgium Dr. Filip van Rickstal Catholic University of Leuven Civil Engineering Department Div. Building Materials Kasteelpark Arenberg 40 3001 Heverlee +3216482797 +3216321976
[email protected]
Cyprus Mr. Christos Efstathiades Public Works Department Republic of Cyprus Ministry of Communication & Works Lefkosia +35799597362 +35725332094
[email protected]
Denmark Mr. Jesper Engelmark DTU - Technical University of Denmark Planning and Management of Building Processes BYG.DTU - Dept. of Civil Engineering BYG.DTU, DTU Building 118, Brovej 2800 Lyngby +45 45251932 +45 45883282
[email protected]
F.Y.R. of Macedonia Prof. Kiril Gramatikov St Cyril & Methodius University Faculty of Civil Engineering Dep of Concrete and Timber Structures UL. Partizanski odredi 24 POB 560 1000 Skopje + 389 2 3116066 ext. 148 + 389 2 3117 367
[email protected]
F.Y.R. of Macedonia Mr. Zivko Bozinovski (Vice Chairman) St Cyril & Methodius University Institute of Earthquake Engineering and Engineering Seismology P.O.B. 101 Salvador Aljende 73 91000 Skopje +389 2176155 +389 2112163
[email protected]
France Prof. Francis Allard Université de La Rochelle Pôle Sciences et Technologie LEPTAB ave Michel Crépeau F-17042 La Rochelle cedex 1 +33 546 45 82 04 +33 546 45 82 41
[email protected]
Germany Mr. Claus Asam TU Berlin Institut für Erhaltung und Modernisierung von Bauwerken Berlin +4930399216 +493039921850
[email protected]
Hungary Dr. Tamás MezĘs University of Budapest for Technology and Economics Muegyetem rkp 3 1111 Budapest +36 1 463 2303 +36 1 463 1638
[email protected]
246
COST C16 Working Group Members
Italy Prof. Roberto di Giulio (Chairman) University of Ferrara Department of Architecture Via Quartieri 8 44100 Ferrara +39 348 3856993 +39 055 244042
[email protected]
Malta Mr. Ruben Paul Borg University of Malta Faculty of Architecture and Civil Engineering Mediterranea, 161, Triq Luigi Billion, Pembroke, Malta Msida, Malta +35679055680 +35621375185
[email protected]
Netherlands Prof. Leo G.W. Verhoef Delft University of Technology Architecture/ Restoration Berlageweg 1 2628CR Delft +31.152784179 +31.152781028
[email protected]
Netherlands Ms. Marie Therese Andeweg Delft Universiry of Technology Faculty of Architecture Berlageweg 1 2628 CR Delft +31152787912
[email protected]
Poland Mr. Alexander Kozlowski Rzeszow University of Technology Building Structure Civil Engineering W. Pola 2 35-959 Rzeszow Poland +48 178541127 +48 178542974
[email protected]
Slovenia Dr. Jana Selih University of Ljubljana Faculty of Civil and Geodetic Engineering Jamova 2 1000 Ljubljana + 386 1 4768575 + 386 1 2504861
[email protected]
Sweden Ms. Sonja Vidén School of Architecture Royal Institute of Technology Stockholm Sweden
[email protected]
COST C16 Working Group Members
247
Working Group 3B Cyprus Mr. Petros Lapithis Art and Design Department Intercollege 46 Makedonitissas Avenue Lefkosia CY, Cyprus +357 22 841 571 +357 22 353 682
[email protected]
Denmark Mr. Torben Dahl Institute of Technology School of Architecture Royal Danish Academy of Fine Arts Philip de Langes Allé 10 1435 Copenhagen +45 32 68 62 04
[email protected]
France Mr. Dominique Groleau Ecole Nationale Supérieure d'Architecture de nantes Laboratoire CERMA rue Massenet 44300 NANTES +33 2 40 59 21 22 +33 2 40 59 11 77
[email protected]
Germany Mr. Frank Ulrich Vogdt TU Berlin Institut für Erhaltung und Modernisierung von Bauwerken Berlin +4930399216 +493039921850
[email protected]
Germany Mr. Christian Wetzel (Vice Chairman) CalCon Holding GmbH Goethestr. 74 80336 Munich +49-(0)89-552698-0 +49-(0)89-552698-75
[email protected]
Greece Prof. Ted Stathopoulos Concordia University / Aristotle University Engineering / Computer Science Centre for Building Studies Building, Civil Engineering 541 24 Thessaloniki
[email protected]
Hungary Mr. András Zöld
[email protected]
Italy Ms. Silvia Brunoro University of Ferrara Faculy of Architecture via Quartieri 8 44100 Ferrara +39 347 1497462 + 39 0532 293627
[email protected]
Malta Mr. Vincent Buhagiar University of Malta Faculty of Architecture & Civil Engineering Environmental Design Department of Architecture & Urban Design Tal-Qroqq MSD 06 Msida +356 2340 2849 +356 21 333919
[email protected]
Netherlands Mr. Christoph Maria Ravesloot Faculty of Civil Engineering and Geo Sciences Department of Design and Construction Section Design and Construction Processes PO Box 5048 2600 GA Delft 31 15 2781472 31 15 2787700
[email protected]
248
COST C16 Working Group Members
Poland Dr. Zbigniew Plewako Rzeszów University of Technology Faculty of Civil and Environmental Engineering Department of Building Structures ul. W. Pola 2 35-959 Rzeszów +48 602759595 +48 178542974
[email protected]
Portugal Mr. Ricardo Mateus University of Minho Civil Engineering Department Azurém 4800-058 Guimarães +351 253 510 200 +351 253 510 217
[email protected]
Portugal Prof. Luís Bragança Lopes (Chairman) University of Minho School of Engineering Building Physics and Construction Technology Laboratory Azurem 4800-058 Guimaraes +351253510200 +351253510217
[email protected]
Slovenia Dr. Marjana Sijanec Zavrl Building and Civil Engineering Institute ZRMK Dimiceva 12 1000 Ljubljana +386 1 280 8342 +386 1 280 8451
[email protected]
Sweden Prof. Dr. Satish Chandra Gothenburg University Institute of Conservation Box 130 St. Nygatan 23-25 40530 Gothenburg +46 31 7734709 +46 31 7734703
[email protected]
This page intentionally left blank
This page intentionally left blank
