Seismic assessment of a RC school building retrofitted with innovative braces

This paper presents the results of a comprehensive numerical study carried out on a Reinforced Concrete (RC) retrofitted school buildings. The as-built structural system consists of spatial RC frames which were designed for gravity load only during the 70's. To enhance the seismic performance and comply the seismic provisions of recently-issued national code, the existing frame was retrofitted through innovative Buckling Restrained Braces (BRBs). Such braces exhibit high ductility, energy absorption and dissipation; they can be reliably utilized either to strengthen RC frames which do not fulfil modern seismic code requirements or for new RC, steel and composite steel and concrete building systems. The seismic performance of the as-built and retrofitted sample structure was investigated through refined static and dynamic analyses, both linear and nonlinear. The benefits of the use of BRBs are expressed in terms of reduced lateral storey deformations, reduction of inelastic demand on beams and columns of the existing framed system and minimization of additional strength demand on the foundation system. It is also shown that such braces can be installed in the existing buildings without interfering significantly with the occupancy, thus lowering the total repairing cost. © 2009 Taylor & Francis Group