Study on the Seismic Energy Response of Seismically Isolated Bridge in High Intensity Area

摘要

In high seismic intensity area, the pier of the isolated bridge remains elastic for frequent earthquake cases, while both the isolated bearing and the plastic hinge of the pier should be considered to undergo inelastic deformations to dissipate seismic energy for rare earthquake cases. In this paper, both the inelastic model and the energy balance equations of the seismically isolated bridge system in high intensity area are established. The lead-rubber bearing is simplified as a bilinear model, and the ductility of bridge pier is considered through the plastic hinge at the bottom of the pier, which is defined by the moment-curvature curve of the bottom of pier. Firstly, the cumulative energy response time histories analyses of a typical seismically isolated bridge for frequent earthquake cases are calculated and the contributing factor of the hysteretic energy by lead-rubber bearing to the input energy is studied. Furthermore, the effect of the initial stiffness K_1 of the lead-rubber bearing on the hysteretic energy contribution and the seismic moment is analyzed, and the analysis results indicate that the seismic moment of the bridge pier decreases and the contributing factor of the hysteretic energy dissipation increases with the decreasing of the K_1 value. Secondly, for rare earthquake cases, the contributing factor of the hysteretic energy dissipation of plastic hinge of the bridge pier and the contributing factor of the hysteretic energy dissipation members including the lead-rubber bearing and the plastic hinge of the bridge pier are calculated. The results show that the lead-rubber bearing dissipates most part of the input seismic energy and the ductility response of bridge pier is limited because of the efficient protection function of lead-rubber bearing.