深厚场地大型桥梁桩基础随机地震反应及可靠性分析

以苏通长江大桥主墩特大型群桩基础为研究背景，考虑地震动的不确定性，将地震激励作为平稳随机过程，采用随机地震反应分析方法，对深厚场地上群桩基础受上部桥墩荷载下的地震反应进行研究。土体动力非线性性能采用等效线性化方法考虑。由于桥墩惯性作用以及软土土层对桩身位移的约束作用，地震激励下桩身位移呈三角形分布。土体位移与土体和基础间距离有关，桥墩-桩-土相互作用对基础两侧1.5倍基础宽度的土体位移有较大影响。桩体内力反应结果表明，桩顶及桩身上部剪力及弯矩均较大，边桩剪力显著大于中间桩剪力。此外，基于强度破坏准则，对以桩身屈服剪力作为控制指标的群桩基础动力可靠性进行了分析。

Stochastic seismic response and reliability analysis of large pile group foundation for bridge on deep overburden layers

The giant pile group foundation of the Su-Tong Bridge located on the Yangtze River is selected to be the subject investigated.The seismic excitation is regarded as stationary stochastic process considering the uncertainties of real seismogram.A stochastic seismic response method,in which the complex response technique is employed,is applied to study the dynamic responses of this pile group foundation with a large pier cap.The dynamic nonlinearity of soils is considered through the equivalent linearity method.During a seismic motion,the displacements along depths of pile shaft appear triangle because of inertia force of pier and weak restraint of soft soil.The displacement of soil is related to the distance between soil and pile foundation.The effects of pier-pile-soil interaction on displacement response of the soil surrounding the pile foundation are significant.The effected range is about 1.5 times width of pile foundation.The internal force responses of piles indicate that the bending moments and shear forces of pile head and upper portion of pile shaft are larger relatively.The shear force of outer piles is marked larger than that of center piles.In addition,based on the principle of intensity damage,the dynamic reliabilities of the pile foundation are analyzed under four different yield shear force levels.