考虑波流影响的深水群桩基础桥墩地震反应分析

用基于ABAQUS软件为平台的平行计算技术,对考虑波流影响的地基土-群桩-桥墩体系进行三维非线性地震反应数值模拟,土体和墩台以八节点等参单元离散,桩以梁单元离散,采用土体黏塑性记忆型嵌套面本构模型描述土的动力特性,采用动力塑性损伤模型描述混凝土的动力特性;基于Morison公式,采用Stokes五阶波浪理论描述表面波流,波浪力以分布力的形式施加于桥墩之上,分析了考虑和不考虑波流作用时不同地震动作用下群桩基础桥墩的地震反应特性,结果表明:波流作用对桩体加速度反应的影响很小,但对桩体相对位移和弯矩的影响显著,波流作用使桩体弯矩和顺流向的相对位移增大、逆流向的相对位移减小,其影响幅度随流速的增大而增大,波流作用与输入地震动特性密切相关。考虑波流作用对深水大型桥梁群桩基础桥墩地震反应的影响是有必要的。

Seismic response analysis of large scale bridge pier supported by pilefoundation considering the effect of wave and current action

Based on the ABAQUS software and the parallel computation technology,a 3-D nonlinear FEM was developed to analyze the seismic response of the foundation soil-pile group-pier system including the effects of water wave and fluid.In the analysis model,the soils were represented by 8 nodes solid elements and the viscous-plastic memorial nested yield surface model was used to describe the dynamic nonlinearity of the soils.The piles were represented by the beam elements and the dynamic plastic-damage model was used to describe the dynamic characteristics of the pile and pier.The Stokes fifth-order wave theory was used to describe the surface water waves.The hydrodynamic pressures acting on the surface of the pile or pier structure were calculated by the Morison's formula.The seismic responses of the foundation soil-pile group-pier system under several measured earthquake ground motions were analyzed by utilizing the presented method and the effects of the water wave and fluid were compared and discussed.It was shown that the water wave and the fluid had a few influences on the acceleration response of the piles but had notable influences on the displacements and internal forces of the piles.The moments and relative displacements in the forward flow direction would be increased under the actions of the water wave or fluid.At the meantime,the relative displacements in the opposite flow direction would be reduced.The effects of the water wave or fluid on the seismic response of the piles would rise with the increase of the water velocity.Therefore,it is necessary to consider the effects of the wave or fluid in the design of the bridge foundations in the deep water.