承台-桩-土作用下铁路桥梁桩基础地震反应

Seismic Response of Pile Foundation of Railway Bridge Considering Cap-pile-soil Interaction

研究目的:低桩承台桩基础是铁路桥梁广泛采用的基础形式,考虑承台-桩-土相互作用效应,对其进行精细化地震反应分析意义重大。以32 m铁路简支梁桥为研究对象,建立考虑承台-桩-土相互作用效应的单墩抗震计算模型,采用反应谱法研究承台侧向土埋深及桩侧土m值取值对桥梁动力特性及桩基础地震反应的影响规律。研究结论:(1)承台侧向土埋深对桩顶位移及桩顶剪力影响显著,增加埋深,能有效降低桩顶剪切破坏震害的发生;(2)承台侧向土埋深对桩身弯矩的大小及分布规律影响显著,随着埋深减小,横向激励下桩身弯矩最值可能同时出现在两个部位,而纵向激励下桩身弯矩最值仅出现在某一个部位;(3)同一种土层,m值取值不同,对桩顶位移及桩顶弯矩影响显著;(4)本研究成果可应用于铁路桥梁桩基础的抗震设计。

Research purposes: Pile foundation with low pile cap is a widely used foundation form of railway bridge.Considering the interaction effect of cap-pile-soil,it is of great significance to carry out refined seismic response analysis. Taking a 32 m simply supported railway bridge as the research object,this paper establishes a single pier aseismic calculation model considering the interaction effect of cap-pile-soil,and studies systematically the influence of cap lateral soil depth and m value of the pile lateral soil on the dynamic characteristics of bridge and seismic response of pile foundation by using response spectrum method.Research conclusions:(1) The lateral soil depth of cap has significant influence on the displacement and shear force of pile top,and increasing the depth can effectively reduce the shear failure of pile top.(2) The lateral soil depth of cap has significant influence on the magnitude and distribution of bending moment of pile body. With the decrease of the lateral soil depth of the cap,the maximum bending moment of the pile body under the lateral excitation may appear in two parts at the same time,while the maximum bending moment of the pile body under the longitudinal excitation only appears in one part.(3) In the same soil layer,different values of m have great influence on the displacement and bending moment of pile top.(4) The research result can be applied to the design of railway bridge pile foundation.