Non-linear bridge response to differential support motions

Three different methods are compared for evaluating the peak values of the pier drifts for an existing bridge model subjected to spatially varying support motions: linear and non-linear Response History Analysis (RHA) and the Multiple Support Response Spectrum (MSRS) method. The RHAs are performed for sets of support motions generated with the method of conditional simulation for a prescribed spatial variability model. In order to make consistent comparisons, the input excitations in the MSRS analysis are described by the same spatial variability model and the mean response spectrum of the simulated motions. The MSRS estimates are compared with the RHA results in order to evaluate the ability of the MSRS method to provide: (i) reliable estimates of the peak linear response and (ii) approximate estimates of the non-linear response employing the equivalent displacement rule.