Seismic Response Analysis of High-Pier Bridge under Near-Fault Multiple Pulse Record Excitation

The multiple pulse effect of near-fault seismic records on the nonlinear seismic response of high pier railway bridges (HPRB) was investigated. First, three representative groups of seismic records, namely, single pulse record (SPR), multiple pulse record (MPR) and none pulse record (NPR) were selected by visual inspection. Second, pulse characteristics were quantitatively identified using wavelet analysis method (WAM) and energy-based approach (EBA) to investigate if impulse ground motion identification method was applicable to MPR. Finally, a typical HPRB, located in the southern region of China, was adopted as the research object, the non-linear finite element model was established in OpenSees platform, and the non-linear seismic response analysis of the HPRB was carried out. The effects of MPR and SPR on the nonlinear seismic response of the HPRB were compared. The results obtained from the analyses indicate that the WAM and EBA are applicable to ground motions with only one dominant pulse in the velocity history, and are not applicable to multiple pulse ground motions. Near-fault MPRs and SPRs pose the risk of stronger damage to irregular high pier bridges than NPRs. Under MPR excitation, the top displacement of pier 1 and pier 2 is, respectively, 118.9% and 109.6% larger than under NPR excitation. The bending moment and the curvature at the bottom of the pier also increase. Near-fault MPR is found to produce pounding force and pounding times that are, respectively, 3−5 times and 2−3 times greater than those by NPR excitation. In the near field multiple pulse earthquake, the main beam is more likely to cause severe impact damage, and thus, the appropriate anti-collision measures should be adopted in seismic design.