Abstract

In Europe, most of the social housing heritage, built before the 1980s, suffers of architectural and functional obsolescence and seismic vulnerability, raising questions about the future of the cities and their inhabitants. In an era of environmental emergency and lack of resources demolition and reconstruction is not a sustainable alternative. A multi-purpose campaign of architectural, functional and structural retrofit is fundamental but the complex information and requirements to handle require integrated and innovative solutions. The bio-mimicry design approach led to the definition of the “building exoskeleton”: an external steel frame, two or three-dimensional, encapsulating the existing building and provided of shape memory alloys-based devices for passive seismic dissipation. The simplicity of the structure gives high flexibility in the definition of the new architectural features and functional performances, adapting to the changing necessities on both space and time scales. The energy performances result also radically improved. The efficiency of this scheme to improve the seismic response of the constructions is verified for a real case study – a concrete frame with brick infill – through static and dynamic nonlinear analyses with the software SAP2000. Finally, the economic and technical feasibility of the proposal is discussed together with the implications of the project and the possible developments.

Speaking about building retrofit in Europe, the attention is often focused on the residential building stock built after the Second World War, which represents the 75% of the total number of buildings present on the territory. Recently many cities are encouraging campaigns of retrofit of the housing heritage built after the Second World War, since, in terms of cost, time, financing, consumption, and sustainability, the practice appears more convenient than building anew. To maximize the benefits of these retrofit campaigns, it is essential to promote multi-purpose and innovative strategies considering contemporarily architectural, functional and structural aspects. In the field of housing, in particular, it is necessary to develop new models able to answer to the new living style of a dynamic society. In fact, today as in the past, one of the downfalls of the housing sector is failing to recognize the human dimension within the designing process. This paper evaluates past architectural practices to achieve adaptability and flexibility in the residential sector and evaluate strategies for integrated retrofit based on two macro-areas: architectural/societal/functional and structural/technological/constructional.

Recently, many cities in Europe are encouraging the recovery of the existing residential heritage. To maximize the benefits of these campaigns, a multi-purpose campaign of architectural, functional, and structural retrofit is essential. Additionally, a fast-changing society requires new living criteria; new models need to be developed to respond to the developing requirements of communities and markets. This paper proposes a method of analysis for 49 residential retrofit projects, a range of “best practices” presented through the definition of strategies, and actions and thematic packages, aiming at reassuming, in a systematic way, the complex panorama of the state of the art in Europe. Each project was analyzed using a data sheet, while synoptic views and tables provided key interpretations and a panorama of strategies and approaches. The analysis of the state of the art showed that lightweight interventions achieved using dry stratified construction technologies of structure/cladding/finishing are a widespread approach to renovation and requalification both for superficial/two-dimensional actions and volumetric/spatial actions. The study also highlights the leading role of the envelope within retrofit interventions. The retrofit approaches appear to reach the greatest efficiency when reversible, because only in this way do they ensure environmentally friendly actions with the possibility of dismantling. The intervention should improve the flexibility of the existing construction with a correct balance between planning for the present and planning for the future.