Seismic Damage Analysis of Long-Span Continuous Rigid-Frame Bridge with High-Rise Pier Considering Pier-beam Pounding Effect Under Near-Fault Ground Motions

A continuous rigid-frame bridge with a span arrangement of (120+220+120) m was selected to investigate the influence of the pounding effect between main girder ends and transition pier on the seismic response and damage condition of the bridge.This work simulated the actual construction process of the bridge in MIDAS/Civil and extracted the real internal force state at the completion stage of the bridge.Based onOpenSees platform,the study developed a dynamic analysis model considering the internal force state,in which the pounding effects at expansion joints were simulated by the Hertz-Damp model.30 near-fault ground motions with forward directivity effect,fling-step effect and non-pulse were selected and inputted along the longitudinal direction of the bridge.The influence of the pier-girder pounding effect on the peak displacement,residual displacement,pounding force and seismic damage of piers was discussed.The difference of seismic response under three types of near-fault ground motions was analyzed.The results show that the girder end of main bridge not only impacts the girder end of approach bridge but also impacts the transition pier top under strong earthquake excitation because the height of the main girder is not equal to that of the approach girder.When the pounding effect is ignored,the displacement of the transition pier may be largely underestimated,especially under the forward directivity pulse and fling-step pulse the displacements are underestimated by nearly 3 times and 5 times,respectively.The pounding effect is the most significant under the fling-step ground motions with which the transition pier is severely damaged and the other piers are moderately damaged.Ignoring the pier-girder pounding effect may has a significant underestimation on the seismic damage condition and post-earthquake residual displacement of the transition pier.