近断层脉冲型地震动作用下大跨斜拉桥地震响应分析  

Effects of near-fault pulse-type ground motions on the seismic responses of a long-span cable-stayed bridge

作　　者：张凡[1,2] 李帅[1,2] 颜晓伟[3] 王景全[1,2] 

机构地区：[1]东南大学混凝土及预应力混凝土结构教育部重点实验室,南京210096 [2]东南大学国家预应力工程技术研究中心,南京210096 [3]上海市市政规划设计研究院,上海200040

出　　处：《振动与冲击》2017年第21期163-172,184,共11页Journal of Vibration and Shock

基　　金：国家自然科学基金(51378110);江苏省"六大人才高峰"第十一批(JZ-007);江苏省研究生科研创新计划(KYLX15_0086)

摘　　要：为研究近断层脉冲效应和土-结构相互作用(SSI效应)对大跨斜拉桥地震响应的影响规律,以苏通大桥斜拉桥为研究对象,采用系统化的集总参数模型表征地基土的动力特性,建立了考虑SSI效应的结构动力数值计算模型,计算分析了破裂前方效应脉冲、滑冲效应脉冲和无脉冲三组近断层地震动作用下结构的地震响应。计算结果表明:相对于塔底固结模型,SSI效应降低了斜拉桥自振频率,并改变了高阶振型的产生次序;近断层地震动作用下,SSI效应可增大主塔位移响应,对其内力有削弱作用,并可降低纵桥向激励时主梁的位移和内力响应,但横桥向激励时,脉冲效应地震动作用下SSI效应明显增大了主梁的响应;脉冲效应地震动引起斜拉桥地震响应明显高于无脉冲地震动,滑冲效应主要影响纵桥向激励时主塔响应以及纵桥向(或横桥向)激励下主梁响应,破裂前方效应对横桥向激励下主塔响应影响更加显著。研究成果可为大跨斜拉桥在近断层地震动作用下的抗震设计提供借鉴。The objective of the study is to determine the seismic responses of the Sutong cable-stayed bridge,taking into account the near-fault pulse-type ground motion effect and soil-structure interaction effect（ SSI）. Systematic lumpedparameter models were adopted to describe the dynamic behavior of the foundation supported on soil. The dynamic finite element model of the bridge considering the SSI effect was established. The seismic responses of the towers and deck subjected to three pulse-type ground motions,i. e. forward-directivity effect pulse（ FD）,fling-step effect pulse（ FS） and non-pulse records,were investigated. The results reveal that SSI effects mainly affect the bridge responses through a systematic decrease of all modal frequencies and a substantial change in the nature of dominant shapes especially for the higher modes of vibrations. When the bridge is subjected to pulse-type near-fault ground motions,the SSI effect causes larger displacements of the towers,a significant decrease in the internal forces of the towers,and a certain degree of reduction in both the displacement and base moment of the girder under longitudinal excitations. However,the response of the girder under horizontal excitations is obviously amplified by the SSI effect. The seismic responses of the cable-stayed bridge under the pulse-type ground motions are significantly higher than that under non-pulse ground motions. Fling-step ground motions amplify the responses of the towers under longitudinal excitations and the responses of the girder under longitudinal or horizontal excitations. Forward-directivity ground motions amplify the responses of the towers under horizontal excitations. The research results could provide a reference for the seismic design of long-span cable-stayed bridge systems located in near-fault zones.

关 键 词：近断层地震动 破裂前方效应 滑冲效应 系统化集总参数模型 土-结构相互作用 大跨斜拉桥 

分 类 号：U448.27[建筑科学—桥梁与隧道工程]