行波激励下桩-土-斜拉桥多点振动台试验  

Multiple Shaking Table Tests on Pile-soil-cable-stayed Bridge Under Travelling Wave Excitations

作　　者：孙利民[1] 谢文[2] 楼梦麟[1] 梁发云[3] 陈清军[1] 袁万城[4] 

机构地区：[1]同济大学土木工程防灾国家重点实验室,上海200092 [2]宁波大学建筑工程与环境学院,浙江宁波315211 [3]同济大学地下工程系,上海200092 [4]同济大学桥梁工程系,上海200092

出　　处：《中国公路学报》2017年第12期221-233,共13页China Journal of Highway and Transport

基　　金：国家自然科学基金项目(91315301;91515101;90915011;51608282);浙江省自然科学基金项目(LY15E080011)

摘　　要：为了研究桩基和场地土以及地震动空间效应对大跨斜拉桥地震反应的影响,以一座试设计主跨1 400m超大跨斜拉桥为试验原型,按1/70几何缩尺比设计和制作了一座包括群桩基础、模型土和上部结构等在内的试验全模型,缩尺后试验模型全长38.2m;根据动力等效原则,采用由砂子和木屑均匀混合而成的模型土模拟场地土,且用层状剪切土箱盛放。采用时间滞后的方法实现行波效应,通过多点振动台试验分别研究了纵向行波、横向行波对超大跨斜拉桥地震响应的影响及其机理。试验结果表明:行波作用对斜拉桥地震响应的影响非常复杂,纵向行波使塔顶纵向加速度和主跨竖向加速度的最大增幅分别约为50%和40%,而横向行波使塔顶和主跨横向加速度的最大减幅分别为15%和50%;纵向行波使主跨竖向位移的最大增幅约为40%,而横向行波使其横向相对位移的最大减幅为20%。行波作用对斜拉桥不同构件地震响应的影响也不同,与一致激励结果相比,纵向行波使塔顶、塔-梁以及墩顶相对纵向位移的最大减幅分别约为50%、40%和60%,使主跨竖向位移的最大增幅约为40%。此外,试验发现桩-土-结构相互作用对主塔、桥墩的加速度响应产生明显不利影响,使塔底增大2倍多,墩底增大1.1~4.0倍。基于上述结果,建议在斜拉桥地震反应分析或抗震设计时,需考虑行波效应和桩-土-结构相互作用等因素的影响,特别是其不利影响。To investigate the influences of the pile foundation, site soil and ground motion spatial variability on the seismic response of long-span cable-stayed bridges, a 1/70-scaled cable-stayed bridge model was designed and constructed according to a trial designed cable-stayed bridge with main span of 1 400 m. The scaled full model included superstructure, pile group foundations and model soil comprising dry sand and sieved sawdust and placed in laminar shear boxes, where the total length was 38.2 m. The travelling wave effect was realized by the time delay of the input wave arriving different supports. The scaled model was tested by the multiple shaking tables array to clarify the mechanism associated with the seismic response of the super long-span cablestayed bridge under uniform and non-uniform excitations in the longitudinal and transverse directions, respectively. The results show that the travelling wave effects have very complex influences on the seismic response of the long-span cable-stayed bridge. There are approximately 50% and 40% increments in the longitudinal acceleration response at the tower top and the vertical acceleration response of the girder under non-uniform excitations, compared with those under uniform excitations in the longitudinal direction. Whereas there are approximately 15% and 50 % reductions in the transverse acceleration response at the tower top and the girder under nonuniform excitations, compared with those under uniform excitations in the transverse direction. The vertical relative displacement of the girder under non-uniform excitations is approximately 40% larger than that of the girder under uniform excitations in the longitudinal direction, while the transverse relative displacement of the girder under non-uniform excitations is approximately 20% smaller than that of the girder under uniform excitations in the transverse direction. Furthermore, the travelling wave effects also have inconsistent influences on the seismic response of various components. There are approximately

关 键 词：桥梁工程 大跨斜拉桥 振动台试验 行波效应 桩-土-结构相互作用 层状剪切土箱 

分 类 号：U442.55[建筑科学—桥梁与隧道工程]