Influence of ground motion duration and isolation bearings on the seismic response of base-isolated bridges

This study investigates the effect of ground motion duration on the seismic response of base-isolated bridges. Three different isolation bearings are considered in this study, such as lead rubber bearing (LRB), Shape memory alloy wire-based lead rubber bearing (SLRB), and Friction pendulum system (FPS). Each isolation system is designed to provide a similar isolation period so that the seismic response is comparable. Using 20 long-duration motions and 20 spectrally matched short-duration records; the seismic performance of the base-isolated bridges is evaluated and compared using nonlinear time history analyses. Response parameters considered for this study are the base shear in the piers, the acceleration of the bridge deck, maximum and residual displacement of the isolation bearings as well as the energy dissipation capacity. The results indicate that the long-duration motions cause more damage to different bridge components as compared to the short-duration motions in-terms of higher deck acceleration, pier base shear, and residual isolator displacement. It is also observed that ground motions having similar magnitude with different significant durations can significantly affect the isolator as well as the bridge response.