动水压力和PSI对深水高墩桥梁抗震性能的影响?

以我国西部地区某库区一深水高墩大跨连续刚构桥梁为工程背景,考虑动水压力、桩-土相互作用以及二者联合作用的影响,确定了六类不同的分析工况,利用OpenSEES源代码分析平台分别建立有限元模型,通过输入两组空间地震波进行非线性时程分析,讨论了动水压力和桩-土相互作用对深水高墩大跨桥梁动力特性和抗震性能的影响。研究结果表明,考虑动水压力和桩-土相互作用会降低高墩大跨桥梁的振动频率,且二者的影响主要体现在下部结构振型参与率较高的高阶模态;动水压力效应会增加高墩在地震作用下的动力响应,但桩-土相互作用对非线性分析结果的影响没有明显的规律;同时考虑动水压力和桩-土相互作用时,深水高墩桥梁的地震响应并不是简单的相互促进或相互抵消,而与地震动的大小、频谱特性等相关;强地震作用下桥梁结构的桩顶水平位移较大时,抗震设计中更适合采用"p—y曲线"法模拟桩-土相互作用效应。

Influence of Hydrodynamic Pressure and Pile-Soil Interaction(PSI) on Seismic Performance of High Pier Bridges in Deep Water

A high pier long-span continuous rigid frame bridge in the western reservoir region of China is taken as the engineering background.The hydrodynamic pressure,pile-soil interaction(PSI) and the influence of their combined effect were considered to determine six different analysis cases.The finite element models of the six analysis cases were established,respectively,by using the source code computational platform OpenSEES.Then,two groups of ground motions were applied to conduct the nonlinear time-history analysis,in order to investigate the influence of hydrodynamic pressure and PSI on seismic performance of high pier long-span bridges in deep water.The results show that the effect of hydrodynamic pressure and PSI can reduce the vibration frequency of the high-pier long-span bridge,and their influence is mainly reflected in high order modes with more participation rates of vibration mode for the substructure.The effect of hydrodynamic pressure will increase the dynamic response of the high piers under earthquake action.However,the PSI effect on the results of nonlinear time history analysis performs no obvious rules.When both of the hydrodynamic pressure and PSI are considered,the seismic response of high pier bridges in deep-water is not simple mutual promotion or offset,but related to the intensity of ground motion,spectrum characteristics,and so on.The "p—y curve" method is more suitable for seismic design to simulate the PSI effect,if the horizontal displacement of the pile top of a bridge structure is larger under strong earthquake action.