Holistic sustainable renovation of Post-World War II reinforced concrete building under a life cycle perspective by means diagrid exoskeletons

Enormous resources are being invested in Europe to foster environmental, economic, and social sustainability; however, such relevant effort to reach ambitious targets may be a missed chance, unless a deep and systematic intervention on the built environment is undertaken targeting sustainability, safety and resilience at the same time. This thesis provide a contribution to the scientific debate, focusing on holistic renovation from outside of reinforced concrete building by embracing a life cycle perspective. Effectiveness of such an approach to the renovation with respect to traditional retrofit actions emerges both in the construction time when addressign the barriers to the renovation such as the inhabitant relocation and the existing buildgin disruption, and when broadening the time frame of the analyses, shifting from the construction time to a life cycle perspective. In this second case, the potential of the holistic approach becomes clear in reducing costs, impacts on the inhabitants and impacts on the environment over the building life cycle. The reults of this new approach is a retrofit solution based on a Life Cycle Thinking, which not only entails the use of recyclable/reusable materials, but also encourages interventions carried out from the outside the buildings, and imply the adoption of reparable, easy maintainable, adaptable and fully demountable solutions with pre-fabricated components, thus guaranteeing, at the end-of-life, the selective dismantling and reuse or recycle of the components to reduce construction waste. The described solutions, which couples structural retrofit in the renovation action, stem as an enhancement of past pioneering “camouflage” interventions, such as double-skin solutions entailing in many benefits such as the protection of human lives, resilience and the lengthening of the existing buildings service life, the repairing costs and building downtime reduction, reduction of the environmental impact associated with seismic risk over the building life cycle and long-term protection of the investment (Marini et al. 2018). Within such a new perspective, new technology options are needed to innovatively combine structural retrofit, architectural restyling and energy efficiency measures; in this work an effective retrofit solution is proposed. Among the possible retrofit solutions the diagrid structures as innovative strenghening technique from outside are investigated. In the first part of this thesis, the state of the art of diagrid design is reported. New criteria for the design of retrofit solution are set, and a design procedure for elastic diagrid is proposed. In the third chapter, a parametric evaluation of the retrofitted system through a simplified 2 DOF system is conducted, and a set of design spectra are defined in order to simplify the design procedure and derive the optimal retrofit parameter for RC buildings. Finally, a reference case study representative of the typical RC building is developed in the fifth chapter of this work to asses and validate the procedure.