近场具有脉冲地层运动的单自由度双线性结构残余位移比谱

遭受近场具有脉冲地层运动的桥梁由于非线性变形桥墩会产生残余位移,给桥梁震后的维修和重建带来困难。运用BISPEC程序,选择45条近场具有脉冲地震记录,进行不同基本周期、延性系数、双线性因子的单自由度双线性结构的时程响应及残余位移比分析。结果表明:不同地震动作用下,单自由度双线性结构的残余位移的离散性很大;场地类型、结构周期和位移延性对残余位移比的影响不大,双线性因子对残余位移比的影响很大;双线性因子大于0.1时残余位移比很小,双线性因子从0.1变到-0.1时残余位移比迅速增加,双线性因子小于-0.05后,残余位移比接近1。针对单自由度双线性结构的设计,提出近场具有脉冲地层运动的残余位移比谱。应用该谱的工程实例分析结果与非线性时程响应的分析结果吻合较好。

Residual Displacement Ratio Spectrum of Single-Degree-of-Freedom Bilinear Structure under Ground Motions with Pulse in Near-Fault Zones

Due to nonlinear deformation of piers,bridge structures subjected to ground motions with pulse in near-fault zones may likely have residual displacements.Residual displacement is undesirable because it presents problems during repair and reconstruction after an earthquake.45 ground motions have been selected,nonlinear time response analyses and residual displacement ratio analyses of a single-degree-of-freedom bilinear oscillator,with different natural period,ductility factors,bilinear factor were carried out by the procedure BISPEC in order to obtain a method of estimating the likely residual displacements of real single-degree-of-freedom structures.Analyses indicated that there was scatter in the normalized residual displacement for different earthquake records.SRDR was not strongly dependent on soil types,natural period and ductility factors.Bilinear factor is the most significant parameter controlling SRDR.SRDR becomes small when bilinear factor is more than 0.1;SRDR increases rapidly when bilinear factor changes from 0.1 to-0.1;SRDR becomes 1 when bilinear factor is smaller than-0.05.A residual displacement ratio spectrum under ground motions with pulse in near-fault zones is presented for the design of single-degree-of-freedom structures and a design application is also provided for engineering examples.The results computed from spectrum correspond to which from nonlinear time response analyses.