Selective dissipative bracing strategy for seismic retrofit of single-room RC buildings

A selective dissipative bracing strategy for single-room reinforced concrete buildings with significant lateral stiffness discontinuity, determined by the presence of infills on the lower façade level and ribbon windows on the second level, is presented in this paper. According to this special architectural layout, typical of a wide stock of Italian buildings belonging to the second half of 20-th century, dampers are installed on the upper level and conventional steel braces on the lower level. Pressurized fluid-viscous dissipaters are adopted as protective devices, in view of their very high specific damping capacity, as well as of their activation capacity from the early seismic response stages. A school gym dating to the mid 1970s is examined as representative case study. The results of the seismic assessment study in current state highlight a significant inelastic response of the infill panels and the RC columns, and very high drifts on the unfilled level, under a Basic Design Earthquake (BDE)-scaled seismic action. The analyses in post-intervention conditions show a remarkable response reduction both in terms of drifts and stress states, consistently with the target design objectives. This allows reaching a safe response of structural elements and ribbon windows, and an elastic response of infills, up to the BDE.