Abstract

This doctoral thesis presents technical strategies for the rational maintenance of the building heritage directed at the integrated retrofit of social housing stocks. The study comprised the analysis of recovered residential buildings in order to develop new sceneries to adopt in critical situations, leading to the definition of a new experimental practice called “adaptive exoskeleton”. This strategy involves the wrapping of the entire original building with a three-dimensional structural envelope, the exoskeleton, using a construction process able to limit interferences on the use of the building and on the life of its inhabitants. The exoskeleton is an independent frame, carefully designed at the joint-scale to achieve awareness of the constructive sequence and of the optimization of the resources. Dry construction technologies resulted to be the most effective, because based on the principles of lightness and reversibility, and because they allow to realize a structural grid able to satisfy different standards in relation to the changing user conditions. The strategy of the adaptive exoskeleton, which exploits optimized and industrialized components, appears convenient in relation to large-scale interventions on the built heritage and, at the same time, it is architectonically versatile, with many possible options adaptable to different cultural contexts. The structural frame can be adjusted to different dimensions, extensions, typologies and technologies, maintaining the same basic characteristics. Passive dissipative devices realized with shape memory alloys, strategically located as connectors with the existing building, are used in order to reduce the lateral displacements during earthquakes. A key idea is the separation between the long lasting elements of the construction, such as the structural systems, and the parts that can be updated progressively in relation to the requirements of the user or to the technological innovations. This principle is convenient in large-scale campaigns, where it is necessary to create a solid base structure without renouncing to the individualization and the variety of the demand, which stimulates the introduction of architectural components with a shorter use-life. The structural characteristics of this construction and its ability to dissipate the seismic input, were analysed during a research period of twelve months undertaken at the Eindhoven University of Technology (Netherlands) at the unit of Innovative Structural Design of the Built environment department. The verification phase considered two building typologies, due to their high diffusion in Europe: the use of the finite element software SAP2000 required the application of a “frame model” for masonry buildings and of a “strut model” for the concrete frame with masonry infill. The seismic behaviour of the buildings was analysed before any intervention and after the introduction of the adaptive exoskeleton implemented with shape memory alloys-based devices. The experimental phase was also undertaken with reference to San Bartolomeo estate in Brescia, Italy. Summarizing, the research underlined the convenience of applying retrofit processes in opposition with demolitions and reconstructions, above all in terms of social and environmental costs. The adaptive exoskeleton, in particular, provides an integrated and synergic solution because while improving the seismic behaviour of the structure, offers additional space for services and functions, increasing the economic value of the building and improving its energy performances and its architectural characteristics.