Seismic response analysis of existing non-ductile buildings retrofitted with BRBs

The paper assesses the seismic performance of typical reinforced concrete (RC) existing framed structures designed for gravity loads only. Such structures exhibit high seismic vulnerability, i.e. low lateral stiffness, strength along with limited translation ductility; thus retrofitting strategies are employed to augment the seismic system capacity. Metallic dissipative braces, namely buckling restrained braces (BRBs), may utilized as cost-effective rehabilitation schemes for existing RC framed buildings. The braces can be conveniently installed along the perimeter frames of the multi-storey buildings to lower the seismic demand on the existing structure and regularize its dynamic response. The design approach assumed herein postulates that the global response of the inelastic framed structure is the sum of the elastic frame (primary system) and the system comprising perimeter diagonal braces (secondary system). Displacement-based approaches were employed to design the BRBs and the needs to improve existing code provisions and design guidelines are emphasized. Analysis and further design research needs, such as the effects of the effects of masonry infill panels and the beam-to-column joint modeling on the seismic performance of the retrofitted frames are also discussed.