Seismic Assessment and Improvement of a RC Gym Building

A seismic evaluation and advanced retrofit design study on a gym with reinforced concrete structure is presented in this paper. The building is representative of the peculiar characteristics of the wide stock of Italian school gyms and sports hall belonging to the decades from the 1960s to the 1990s, among which the continuous masonry infills placed in contact with the frame structure, and the ribbon windows situated in the upper portion of the side façades. The assessment study in current state is carried out via non-linear dynamic analyses, modelling the infills by means of equivalent diagonal struts, and the reinforced concrete members by plastic hinges. The response of the ribbon windows, not expressly modelled in the analysis, is checked in terms of corresponding inter-level drift. The results show significant damage to the infill panels and the RC columns, and very high drifts at the windows level, and thus their potential collapse, for the Basic Design Earthquake (BDE)-scaled seismic action. Consequently, a seismic retrofit hypothesis is proposed, based on the installation of a dissipative bracing system incorporating pressurized fluid-viscous devices at the windows level, and conventional braces on the lower level. The analyses in post-intervention conditions highlight a remarkable response reduction in terms both of drifts and stress states, preventing damage in the structural and non-structural elements up to the BDE, with no architectural intrusion and interruption in the usage of the building.