Multi-objective optimization design method of RC double-column bridge piers with cable-pulley based self-centering energy dissipation (CP-SCED) braces

Abstract

Recently, the authors introduced a parameter-adjustable cable-pulley based self-centering energy dissipation (CP-SCED) brace to mitigate seismic induced damage of reinforced concrete (RC) double-column bridge piers. With this novel brace, the parameters that could significantly influence the structural seismic responses, such as yield strength, post-yield stiffness, and energy dissipation ratio, can be conveniently adjusted. The inherent multi-parameter nature of the brace together with various structural damage indices pose challenges in the brace design. This study aims to develop an optimization design method to determine the brace parameters that achieve a balanced performance across different design objectives, including the peak drift ratio, residual drift ratio, peak acceleration response of the braced pier, and the brace peak axial force. This design framework involves a few key steps, which encompass establishing the restoring force model of the braced structure, performing multi-parameter optimization design using the non-dominant sorting genetic algorithm II (NSGA-II), and judging and verifying the optimization results. The results indicate that the brace designed based on the proposed optimization method fully utilizes its hysteretic behavior, thus effectively enhancing the seismic performance of the bridge pier under earthquake loading. Considering the versatility of the method, the proposed optimization framework has the potential to be applied to other complex systems that are challenging to design using traditional methods.