Seismic fragility analysis of a long-span cable-stayed bridge equipped with a horizontal bidirectional hybrid damping system

This study evaluates the longitudinal and transverse seismic fragility of a long-span bridge equipped with a novel integrated Horizontal Bidirectional Hybrid Damping System (HBHDS). The HBHDS is composed of eddy current dampers, metallic yielding dampers, fuse-lock devices and a spherical steel bearing. A total of 100 ground motions are selected and the damage states of critical components i.e., bearings, towers and piers are defined. Seismic fragility curves for the bridge equipped with the HBHDS are generated at both the component and system levels. Fragility mitigation effects are assessed and compared with those related to the damping system applied to the actual bridge. The results indicate that, at the component level, the proposed HBHDS can achieve a comparable seismic fragility control effect with respect to the as-built bridge configuration in the longitudinal direction. It is also less vulnerable to side pier and tower failure than the transverse fixed system. For the system-level seismic fragility, the HBHDS is the best performer in terms of mitigating the failure probability of a long-span cable-stayed bridge, highlighting superior performance in the longitudinal and transversal direction.