液化场地桩-土-结构动力相互作用的有限元分析

Finite element analysis of pile-soil-structure dynamic interaction in liquefiable site

基于Biot两相饱和多孔介质动力耦合理论,采用有效应力方法对液化场地桩基础的地震反应进行了三维有限元分析。在饱和液化砂土的循环塑性模拟中,采用了超固结边界面、Armstrong-Frederick型非线性运动硬化准则和非关联流动准则来描述动荷载作用下砂土的循环活动性以及液化强度等特性。对于桩的动力本构行为,则采用了可以考虑体积效应和轴向力影响的梁—柱单元来模拟。以某城市高架桥的实际工程为例,应用该方法对地基液化时桩—土—结构的动力相互作用进行了计算分析,并得到了一些有用的结论。

Based on Blot's dynamic coupled theory for two-phase porous media, the earthquake response analysis for pile foundations was dealt with by a three-dimensional effective stress finite element method. Liquefiable saturated sand was simulated by a cyclic elasto-plastic constitutive model, which was mainly composed of overconsolidation boundary surface, Armstrong-Frederick type nonlinear kinematic hardening rule and non-associated flow rule, to describe the response features under seismic loading, such as cyclic mobility, liquefaction strength and so on. For the dynamic behaviour of piles, a beam-column element was used for considering the axial force-dependency as well as the volume effect. Subsequently, with the proposed method, an actual urban elevated highway bridge was illustrated involving a group-pile foundation subjected to seismic excitation in the saturated liquefiable deposits. From the simulated result, some fundamental aspects of pile-soil-structure dynamic interaction in liquefiable site were investigated to yield useful results for design.