Preliminary fragility analysis of a r.c. frame school building retrofitted by an external dissipative system

Seismic events occurred in the last decade in Italy led the attention to the evaluation of the health and need of interventions on the existing school buildings heritage, whose collapse or loss in functionality after an earthquake may lead to significant economic and social losses. For this reason, this study focuses on the preliminary fragility assessment of a typical school r.c. frame building, retrofitted through an external configuration based on the use of fluid viscous dampers (FVDs). The case study is a two elevations moment resisting frame structure, built in Italy in the sixties without seismic code. The external retrofit configuration is a rocking base system consisting of a pinned-rocking braced frames equipped with fluid viscous dampers at their base. Fragility curves, built by accounting for different level of inter-storey drift and for seven intensity measures of the seismic action, provide useful insights about the efficiency and dynamic response of the r.c. frame before and after the retrofitting works.