Quantitative Assessment of Seismic Retrofit Strategies for RC School Buildings Using Steel Exoskeletons and Localized Strengthening

This study offers a quantitative performance assessment of integrated seismic retrofit designs applied to an in-service 1960s reinforced concrete school structure in Central Italy. The research combines in-depth experimental material characterization with complex numerical simulations in order to estimate both the independent and interaction effects of external steel exoskeletons in conjunction with localized CAM (Cucitura Attiva dei Materiali) strengthening. The experimental investigation includes extensive material characterization through core drilling and non-destructive pacometric inspections to accurately define the existing concrete properties. The numerical analysis is performed with Finite Element modeling to estimate four different structural conditions: the original state, the condition with static strengthening, the condition with additional steel exoskeletons, and the condition with both exoskeletons and localized CAM reinforcements. The results quantitatively estimate the specific performance gains from the individual retrofit strategies. The steel exoskeletons show effective reduction in inter-story drifts but negligible effect on strength-oriented failure mechanisms. Localized CAM strengthening therefore stands out as necessary in reaching adequate safety levels in all the failure mechanisms. Economic analysis reveals that while steel exoskeletons provide the major cost component, the integrated approach with localized strengthening is essential for achieving comprehensive seismic safety enhancement.