Residual Displacement In Performance-based Seismic Design Of Bridge Pier

Structures subjected to ground motions may likely have residual displacements. Residual displacement is hoped to be limited to extent level because there is some matters during repair and reconstruction after an earthquake. A single-degree-of-freedom bilinear oscillator, with different natural period, ductility factors, bilinear factors, using 45 ground motions with pulses in near-fault sites and 40 ground motions with not pulses in normal sites were investigated in this paper. These analyses were carried out in order to obtain a method of estimating the likely residual displacements of actual single-degree-of-freedom structures with bilinear stiffness. The results of analyses indicated that the ground motions, but trends in behavior were dominated by the post-yield stiffness. Both residual displacement ratio spectra under ground motions with pulses recorded in near-fault sites or with non-pulses recorded in normal sites are developed for seismic design of a single-degree-of-freedom structure and the deviation was scattered in the normalized residual displacement for different earthquake records of ground motions and the design application is also presented for engineering case. The results computed from the residual displacement spectrum are compared with those computed using step-by-step time nonlinear response analyses and it was shown the proposed procedure generally gives a better estimation.A fragility curve for bridge pier generated through nonlinear static analysis method was investigated in this paper, which took spectral acceleration S_a as ground motion intensity measures IM and residual displacements as engineering demand parameter EDP. Measures for mitigating residual displacements were introduced at last. Experience after earthquakes had noted that: not only maximum displacement but residual displacement should be considered in seismic design and evaluation.