NONLINEAR SEISMIC RESPONSES OF ISOLATED BRIDGES OF LRB WITH BI-DIRECTIONAL COUPLED MODEL

In order to investigate the nonlinear seismic responses of isolated bridges with lead rubber bearings (LRB) under a bi-directional horizontal earthquake excitation, a bi-directional coupled elastic-plastic model of LRB under two horizontal orthogonal directional excitations was established, and the unidirectional force-deformation behavior skeleton curve of this bi-directional coupled elastic-plastic model is considered to be bilinear. Based on the bi-directional coupled elastic-plastic model of LRB, an analytical model of nonlinear seismic responses of continuous multi-span isolated bridges with LRB and its solving method were carried out. Finally, the comparison of the calculation results of nonlinear earthquake responses obtained by considering and ignoring the bi-directional coupled interaction of bearing restoring force is made for one example of the isolated bridges with LRB. It is shown that the bi-directional coupled interaction of the restoring forces of LRB has considerable effects on the seismic responses of the isolated bridge. If these couple interaction effects are ignored, then the peak bearing displacements are underestimated, which can be crucial for the design of isolated bridges.