Seismic retrofit of existing school buildings in Italy: Performance evaluation and loss estimation

The seismic vulnerability and inadequate behaviour of existing school buildings observed during past earthquakes in Italy have raised awareness of the need to upgrade their performance. This paper examines different retrofit strategies for three case study school buildings, representing the main typologies found within the Italian school building stock. The three building typologies investigated in this study are representative of reinforced concrete (RC), precast concrete (PC) and unreinforced masonry (URM) school buildings. A seismic performance assessment was carried out using detailed numerical models that consider the main structural deficiencies documented for older buildings in Italy, generally designed and built before the 1970s. The retrofit interventions were specifically aimed at mitigating these main structural deficiencies in order to meet current building code limit state requirements. These requirements are set to limit the damage to non-structural elements and prevent non-ductile failure mechanisms in the structural system, following a typical building code and practitioner-oriented process. The retrofit alternatives were then evaluated through increasing ground shaking intensities to quantify risk-based decision variables, such as the expected annual loss and mean annual frequency of collapse. The results highlight the level of adequacy of each retrofit option in reducing both the economic losses and collapse vulnerability. To predict the economic feasibility of these interventions, a cost-benefit analysis was also conducted using estimated implementation costs of each retrofit alternative. Lastly, the results were also compared with the outcome of the seismic risk classification guidelines, recently proposed in Italy.