Seismic upgrading of an RC frame building using double-stage yield buckling-restrained braces

Abstract

Nowadays, a large number of existing reinforced concrete (RC) structures require strengthening to meet the new building functions and enhanced seismic demands. Double-stage yield buckling-restrained braces (DYBRBs), capable of yielding at different seismic intensities, offer a promising solution for seismic upgrading. This study presents a performance-based seismic retrofit design method for existing RC structures incorporating DYBRBs. A case study involving the seismic retrofitting of a community hospital converted from an existing public service center building was presented using the proposed method. Three retrofitting schemes were discussed, including the combination of BRBs and viscous damping walls (VDWs), series-type DYBRBs and VDWs, and parallel-type DYBRBs and VDWs. Nonlinear time-history analysis was conducted to compare the response mitigation effect and energy dissipation capacity of three retrofitting schemes. For the investigated structure, the series-type DYBRB exhibited better base-shear reduction under frequent earthquakes, whereas the parallel-type DYBRB achieved better control of inter-story drift and shear force under moderate and rare earthquakes due to higher hysteretic energy dissipation. The incorporation of VDWs further enhanced the overall seismic mitigation effectiveness by providing supplemental damping and suppressing the stiffness-induced amplification of shear-force responses.