考虑桩-土作用的高速列车-桥梁地震响应分析

Seismic response analysis of high-speed vehicle-bridge considering soil-structure interaction

基于空间梁单元有限元法,建立了两种高速铁路多跨简支梁桥的全桥空间分析模型,一种是包括桩基的列车-桥梁模型,给出成层土的动力阻抗,采用改进的Penzien模型模拟桩-土作用;一种是不考虑桩-土作用的墩底固结的列车-桥梁模型;分析了两种模型的自振特性,计算了两种模型在不同车速、墩高、地震强度、不同地震波等工况下的地震反应。计算结果表明,桥梁横向位移、加速度主要受到低频成分的影响,这部分频率与其底部地震波相互反馈,改变了地基运动的频谱组成,使接近于桥梁结构自振频率的分量获得加强,考虑桩-土作用后,横向位移/加速度增加较大;桥梁竖向振动频率受桩-土作用影响较小,随墩高和车速的增加梁体竖向位移增加不大,梁体竖向加速度受高频成分的影响较大,这些高频主要由车辆荷载和轨道不平顺引起。

Based on the finite beam element method,two kinds of whole bridge models of high-speed railway multi-span simply-supported bridge are set up.One is vehicle-bridge model including pile foundation,the dynamic impedances of the layered soil are presented,the improved Penzien model is used to simulate the soil-structure interaction（SSI）;the other is vehicle-bridge model where pier bottom is consolidated without considering SSI;the seismic responses of the models are computed at different vehicle speeds,pier heights,earthquake strengths and earthquake waves.The calculation results show that the influence of the SSI on seismic responses of high-speed vehicle-bridge on soft foundation can not be ignored;the lateral displacement and acceleration of the bridge are influenced by low-frequency components,those low-frequency components interact with the earthquake wave incident from bottom side of the piles,which change the spectrum composition of the foundation movement,the frequency components which approach to bridge vibration frequency are strengthened;the lateral displacement and acceleration of bridge increase a lot after considering SSI;the vertical vibration frequency of the bridge changes little while considering SSI;the vertical displacement of the boxing girder increases little with the increase of pier height and vehicle speed;the high-frequency components which are caused mainly by the vehicle load and the track irregularity significantly influenced on the vertical acceleration of the boxing girder