Nonlinear response of continuous girder bridges with isolation bearings under bi-directional ground motions

The isolation seismic technology has been developed during the past three decades, but it is a current focus in bridge seismic research and practice. In order to investigate the nonlinear seismic responses of isolated bridges and evaluate the effects of seismic isolation on the peak response of the bridges with lead rubber bearings (LRB) under bi-directional horizontal earthquake excitation, an analytical method of nonlinear seismic responses of continuous multi-span girder bridges with LRB and its solving method are presented considering the interaction between the restoring forces of the bearings. Shaking table test of 1/10 the scaled model of two-span girder isolated bridge with LRB have been conducted to verify effectiveness of the LRB as a seismic isolation device and peak response of isolated bridges. Experimental results well agreed with the results obtained from analytical results of peak displacement and acceleration of deck, displacement and force-displacement hysteresis loops of isolators. It is verified that analytical method given this paper is right and effective when analyzing nonlinear earthquake response of continuous girder isolated bridges with LRB. Moreover, the bi-directional coupled interaction of the restoring forces of LRB should be taken into account, which has considerable effects on the peak seismic responses of the isolated bridge