Enhancing seismic performance of multi-story double-column reinforced concrete tall bridge bents utilising an efficient buckling-restrained bracing system

Double-column reinforced concrete (RC) tall bridge bents are typically designed with multiple link beams to enhance lateral stiffness, which also facilitates the installation of buckling-restrained braces (BRBs) for seismic retrofitting. However, the addition of multiple BRBs to tall bridge bents may introduce additional force demands and potential damage to the foundations during earthquakes. This study proposes an efficient BRB system for tall bridge bents, where conventional concrete link beams are replaced with pinned links. The results from nonlinear time history analysis indicate that, when multiple BRBs are installed, the foundations may sustain severe damage before the bent columns during earthquakes. In contrast, the proposed BRB system effectively protects the foundations from significant damage. The advantages of the proposed BRB system are further supported by seismic fragility analysis results. As a seismic retrofit measure, the conventional BRB system can even increase the system-level seismic vulnerability compared to the unbraced system, due to the negative impact of multiple braces on the foundations. The proposed bracing system demonstrates significant effectiveness as a seismic upgrade, considerably reducing the probability of damage to the overall bridge bents.