Seismic vulnerability and isolation bearing optimisation in curved continuous beam bridges

Lead–rubber bearings (LRBs) are used in seismic isolation for bridges, yet optimising their mechanical parameters to enhance seismic performance remains an unresolved challenge. Current methods lack a systematic approach to parameter optimisation that effectively balances bridge component vulnerabilities under seismic loads. Here, a mechanical parameter optimisation framework tailored for bridge seismic isolation bearings is proposed. Using a finite-element model of a three-span curved beam bridge, seismic vulnerability curves for both the bridge components and the entire system were plotted based on the incremental dynamic analysis method. Non-linear time history analysis was then employed to determine the mechanical parameter ranges for the LRBs. Subsequently, the Box–Behnken response surface design and a genetic algorithm were used to optimise these parameters, with the system's seismic vulnerability as the optimisation objective. The results demonstrate that the pre-yield stiffness, post-yield stiffness and yield force of the LRBs influenced the seismic response of the curved continuous beam bridge. The optimised parameters, when K₁ = 12.53 kN/mm and Q = 187.65 kN, minimised the damage probability of the bridge pier. Although the bearing displacement increased, the overall seismic performance of the bridge improved due to reduced pier displacement and controlled vulnerabilities. This outcome confirms the effectiveness of the proposed optimisation framework.