Abstract:Based on non-classical damping problem during simplified analysis process of seismic response for isolated continuous girder bridges, taking lead rubber bearing(LRB) for example, direct integration time-history method and modal time-history method after forced uncoupling are employed to study the effect of non-classical damping on seismic response, and structural modal damping ratios are obtained from equivalent damping ratios of isolators according to linear hysteretic damping model, then compared with non-linear time history analysis, simplified analysis based on response spectra method is adopted to calculate the seismic response. The results indicates that non-classical damping produced by seismic isolation devices changes the overall damping characteristics of structure and its contribution to structural seismic response rises with increased equivalent modal damping ratio, and seismic response obtained by simplified analysis after equivalent linearization of isolators is not safe for lower estimate of pier force and beam displacement.