考虑地震动变异性的大跨桥梁地震响应分析

Seismic Response Study of Long-span bridges Considering the Variability of Ground Motion

在对大跨度斜拉桥进行地震响应分析时,必须考虑地震波到达各墩基础的时间延迟,以及场地地质条件和传播路径造成的地震波幅值、频率等特性的改变。基于三角级数法合成四条具有空间变异性的地震波,采用有限元软件Midas/Civil建立苏通大桥主桥模型,输入地震波模拟桥梁的地震响应,运用相对运动法对该桥进行行波激励和考虑复相干效应的多点激励响应分析。结构响应的数据分析表明:多点激励作用下结构内力和跨中挠度较行波激励小,而左右主塔的塔顶位移较行波激励大;地震不同波激励方式会对结构响应产生较大影响,在分析中应予以充分考虑。

While studying the seismic response of Long-span cable-stayed bridges, the delay of arriving time of seismic wave at different piers, and the change of seismic characters caused by geological conditions and travelling path must be considered. With the aid of Trigonometric series method, four seismic waves with spatial variability were composed,the finite element model of Sutong Bridge by Midas/Civil was built, and the seismic response to Sutong Bridge under multi-support excitation was studied with relative motion method. According to the result, the force and Mid span displacement under the multi-support excitation is smaller than that of travelling-wave excitation, but the displacement of the top of towers is larger than that of travelling-wave excitation. The types of excitation have great influence on both displacements and forces of the bridge structures, therefore, they should be considered.