高速铁路桥梁-桥墩-桩基础-地基耦合系统的地震反应

Seismic Response of Coupled Bridge-pier-pile-foundation on High-speed Railway

摘要:

高速铁路中的桥梁常采用灌注桩基础以控制沉降,地震作用是桩基础的设计工况之一。建立桥梁-桥墩-桩基础-地基为一体的耦合系统非线性三维数值分析模型,以典型地震波为输入,考虑上部结构和基础的共同工作、土-结构动力相互作用、材料非线性和土层对桩的侧阻及端阻作用,开展三向地震作用下的动力有限元计算,并对地基主要土层压缩模量、桩体材料弹性模量、桩径和桩长进行参数敏感性分析。计算结果表明:现行的桩基础设计方案能有效控制地震荷载作用下桥梁的变形;地震过程中的不同时刻,桩侧阻发挥程度不同且不可忽略,以单纯的梁单元模拟桩的动力学行为的适用性值得商榷;桩长和地基主要土层压缩模量对桥梁地震反应影响最大,桩体材料弹性模量的影响次之,桩径的影响最小。

Abstract:

Cast-in-place piles are generally chosen as the foundation for high-speed railway bridges to control settlement.One of the working conditions for the pile foundation design is seismic action.A three dimensional coupled nonlinear bridge-pier-pile-foundation numerical model was established using the typical earthquake record as the input excitation.The combined effects between superstructure and foundation,dynamic soil-structure interaction,material nonlinearity,side skin friction between pile and soil layers,and pile base resistance were taken into account in a dynamic finite element analyses that considered three-dimensional seismic actions.Parameter sensitivity analyses of the compression modulus of the major soil layer in addition to the elastic modulus of the pile material,pile diameter,and pile length were performed.Results showed that the design of the pile foundation can effectively control the deformation of a bridge under earthquake conditions.Side skin friction differed during earthquakes and cannot be neglected.The suitability of pile dynamic behaviors modeled by beam element is open to discussion.The dynamic response of a bridge was influenced mainly by pile length and the compression modulus of the major soil layer and,secondly,by the elastic modulus of the pile material.Pile diameter had no prominent impact on the dynamic response of the bridge.