双薄壁高墩曲线连续刚构桥地震响应分析

seismic response analysis of continuous rigid frame curved bridge with double thin-walled high pier

为确定双薄壁高墩曲线连续刚构桥的自振特性和最不利地震激励方向,以某大跨径双薄壁高墩曲线连续刚构桥为实例,对其进行了自振特性和地震响应分析。应用MIDAS/Civil有限元软件建立了该桥空间有限元计算模型,采用数值仿真方法研究了墩底边界约束、曲率半径对该高墩曲线连续刚构桥结构自振特性的影响,探讨双薄壁高墩曲线连续刚构桥动力特性,并按照最不利地震激励方向分析双薄壁高墩曲线连续刚构桥的地震响应。计算结果表明:对于高等级公路中的曲线半径较大的双薄壁高墩曲线连续刚构桥,曲率对桥梁的自振特性影响很小;曲线连续刚构桥第1阶振动模态一般为纵飘,考虑桩土结效应后其基本周期增大;以曲线桥割线方向和垂直割线方向作为双薄壁高墩曲线连续刚构桥的纵向、横向地震动的主要激励方向,其它地震动输入方向可作为曲线连续刚构桥地震响应分析的补充。

To understand free vibration feature and most unfavorable seismic excitation direction of continuous rigid frame curved bridge with double thin walled high pier, taking a long span continuous rigid frame curved bridge with double thin walled high pier as an example, the free vibration feature and seismic response were analyzed. Using FEA software MIDAS, bridge structural spatial finite element model was introduced. Through analyzing the influence of pier bottom boundary constraint, radius of curvature on bridge＇ s natural vibration characteristics, the dynamic features of the bridge were explored. At last, based on the most unfavorable seismic excitation direction, seismic response of continuous rigid frame curved bridge with double thinwalled high pier was analyzed. It indi cates that the effect of curvature radius is not great for continuous rigid frame curved bridge with a large radius of curvature and double thinwalled high pier in the highway. Its first order vibration mode is longitudinal drift in gen eral. And fundamental period is increased because of the effect of pile soil structure. The seismic excitation direc tion may adopt secant direction and vertical secant direction as the main longitudinal and transverse excitation direc tion. The other directions may be taken as supplement of seismic response analytsis.