深水高桩基础桥梁地震水动力效应分析

Seismic Hydrodynamic Effects on Group-pile Foundations with Caps Merged in Water

摘要:

针对我国深水桥梁建设中广泛采用大型群桩基础的现实情况,为满足深水桥梁抗震分析和抗震设计的需求,进行了深水高桩基础桥梁地震动水力效应的研究.将深水高桩基础的承台理想化为一个浸入水中的截断圆柱体,建立了截断圆柱体的地震动水压等效附加质量与等效附加阻尼矩阵的计算方法,提出了非圆柱体等效为圆柱体的近似处理方法.在频域建立了深水高桩基础桥梁考虑动水力效应的地震振动方程.运用所提出的方法完成了有限元程序编制,并对一座跨海峡大桥进行了地震反应计算.结果表明，地震动水力效应对深水高桩基础桥梁的地震反应有重要影响,因计算的反应量不同,可能使地震反应增大,也可能使地震反应减小,影响幅度可达20%以上.

Abstract:

To meet the seismic design demands of bridges in deep water in China,an investigation was made into the hydrodynamic effects on seismic response of bridges.The cap of group-pile foundation was idealized as a truncated cylinder at first,and theoretical solutions of the added mass matrix and the added damping matrix for the truncated cylinder were developed.Approximate methods were proposed to obtain the added mass matrix and the added damping matrix for the truncated prism with arbitrary section by modifying the ones for truncated cylinder.The seismic motion equation was developed for bridges with group-pile foundation in deep water in frequency domain,and a software was coded for the computation of seismic response of bridges in deep water.The seismic responses of a bridge were obtained by the proposed methods and the software.The results show that the hydrodynamic effects may increase or decrease the seismic response by a percentage of ±20%.