冲刷条件下的桩基桥梁振动台试验  

Shake Table Test of Pile Supported Bridge Under Scour Condition

作　　者：商宇[1] 叶爱君[1] 王晓伟[1] 

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

出　　处：《中国公路学报》2017年第12期280-289,共10页China Journal of Highway and Transport

基　　金：国家重点基础研究发展计划("九七三"计划)项目(2013CB036302);国家自然科学基金项目(51278375)

摘　　要：为了研究河床冲刷效应对自由场和桩基桥梁地震反应的影响,设计并完成冲刷条件下的桩基桥梁振动台试验。试验采用了层状剪切土箱,场地采用均一砂土土层来模拟,其相对密实度约为50%。桩基桥梁试件为2×2群桩基础单墩结构,墩顶固定4t的钢质量块来模拟桥梁上部结构,结构整体的一阶周期约为0.5s。试验共分为自由场、小冲刷深度试件和大冲刷深度试件3个工况,冲刷深度变化范围为0~8倍桩径。试验采用白噪声输入得到了场地和结构的特征周期,并通过Chi-Chi地震实测记录研究了场地土和结构的地震反应。结果分析阶段主要通过加速度计、位移计以及应变片的结果,分析了场地土和结构的动力特性、场地土的加速反应、结构的加速反应和曲率分布等。试验结果表明:冲刷条件下桩基桥梁的地震反应会受到结构和场地土2个因素的影响;场地土层会对基岩的地震动产生显著的放大效应;随着冲刷深度增大,桩基桥梁地震反应的最不利位置由桥墩向桩基础转移,且群桩基础的首次屈服位置会由桩身向桩顶转移。To investigate the effect of scouring on the seismic response of free field and the bridge with pile foundation, ; shake table test on pile supported bridge was designed and conducted. A laminar shear box was used in the test, filled with uniform layers of sand to simulate the site. The relative density of sand was about 50 %. The specimen was a single pier structure supported by a 2 by 2 pile group. A 4-ton steel block was fixed on the top of pier to simulate the superstructure, resulting in a primary period of 0.5 s. There were three test cases including the free field test, small scour depth specimen and large scour depth specimen with a range of scour depth from 0 to 8 times of pile diameters. In the tests, the white noise input was deployed to get dynamic properties of soil and structure, whilst the Chi-Chi earthquake ground motion record was used to investigate the seismic response of soil and structure. The data got from accelerometers, displacement transducers and strain gauges, were used to analyze the dynamic properties, acceleration time history of soil and structure and curvature distribution of structure. The results show that under the scouring condition, the soil and structure are the two key factors which would control seismic behavior of pile supported bridge. Soil layers have an amplification effect on the earthquake input comes from bedrock. With the increase of scour depth, the critical section of bridges with pile foundation transfers from pier to pile foundation. In addition, the first yielding region on the pile transfers from the middle part of pile to the top of pile.

关 键 词：桥梁工程 桩基桥梁 振动台试验 冲刷 场地放大效应 

分 类 号：U442.55[建筑科学—桥梁与隧道工程]