Requalification of RC Frame Apartment Buildings: Comparison of Seismic Retrofit Solutions Based on a Multi-Criteria Approach

Increasing environmental concerns are leading to measures and incentives aimed at reducing the energy consumption of buildings, which must be accompanied by substantial mitigation of seismic and structural risk. As for technical issues, it is important to select effective solutions specifically for medium-size RC apartment buildings (e.g., 3–6 storeys), which is where a large share of the Italian population lives today. To this end, it is important to compare, among other factors, the direct and indirect costs related to alternative techniques, thus allowing stakeholders (mainly private) and designers to select the most suitable solution for each case at hand and, finally, to speed up the design process. In this paper, different seismic strengthening techniques are designed and applied to a case study RC frame building that is representative of the EU building stock. An in-depth comparison is made with the aim of showing the advantages and disadvantages of different choices, mainly based on required costs and possible disruptions, keeping the targeted structural performance equal. Specifically, the possibility of disruption is a key point in hastening or, more frequently, hindering the implementation of the decision. In fact, people’s hesitation to leave their home, as well as the difficulty and high costs involved in finding temporary apartments if many people are involved, generally prevent such interventions from taking place. For this reason, some state-of-the-art techniques—that have minimum impact on non-structural elements, that can be applied only on the outside, and that can still provide an effective seismic retrofit—are examined and critically compared in the paper through a multi-criteria decision-making method.