Seismic Performance Deterioration of Friction Pendulum Isolated Bridges: A Time-Dependent Study under Marine Corrosive Environments

To investigate the time-dependent seismic performance degradation of offshore bridges isolated with friction pendulum bearings, a medium-span isolated bridge exposed to a marine environment is numerically analyzed. A nonlinear dynamic model is developed considering the deterioration of pier columns, bearings, and their combined degradation due to seawater corrosion. Time-history analyses under these three deterioration scenarios are performed to evaluate the evolving seismic responses. The results indicate that isolated pier deterioration has a relatively minor impact on the overall seismic response. In contrast, deterioration of the friction pendulum bearings significantly increases the seismic demand on the pier columns and leads to a pronounced reduction in the hysteretic energy dissipation capacity of the bearings. Among all scenarios, combined deterioration of both piers and bearings results in the most substantial increase in pier-top displacement and pier-bottom moment-rotation hysteresis area, alongside the greatest decrease in the shear displacement capacity of the isolation bearings. These findings highlight the compounded adverse effects of corrosion-induced degradation on the seismic performance of isolated bridge systems.