考虑实际场地的矮塔斜拉桥非线性地震响应分析

为研究场地条件对矮塔斜拉桥非线性地震响应的影响,明确空间变异场地条件对矮塔斜拉桥抗震性能分析的重要性,采用不同场地条件下的抗震设计反应谱作为目标谱,从PEER数据库选择与不同场地反应谱兼容的实测地震记录。以一座主跨为176 m的矮塔斜拉桥为例,基于OpenSEES建立三维非线性有限元模型,对该桥梁进行一致激励和多点激励下的非线性地震响应分析,详细研究空间变异场地条件对矮塔斜拉桥抗震性能的影响。研究结果表明:在一致场地条件下,随着场地变软,矮塔斜拉桥的地震响应逐渐增大,与硬场条件相比,中硬场地和软场地震作用下,塔顶位移将分别增大1.80和3.93倍;不规则场地条件引起的地震动空间变异性使得矮塔斜拉桥的地震响应显著增大,即使与一致场地条件下的最不利的情况相比,实际场地条件下的桥梁结构的地震响应都比其增大84%;在矮塔斜拉桥抗震设计时应当充分考虑空间变异场地条件的影响,采用一致场地条件对矮塔斜拉桥进行抗震性能分析时将低估桥梁的地震需求。

Nonlinear seismic response analysis of extradosed cable-stayed bridge considering actual site condition

In order to study the effect of site conditions on the nonlinear seismic response of extradosed cable-stayed bridge(ECSB)and determine the importance of spatial variation site conditions for the seismic performance analysis of ECSB,the response spectrum of seismic design under different site conditions was firstly taken as the target spectrum.The natural seismic records matched with the response spectrum of different site were selected from the PEER database.Then,a typical ECSB with main span of 176 m was taken as example.The three-dimensional nonlinear finite element model of the bridge was established based on OpenSEES platform.The nonlinear seismic response of the bridge under uniform and multi point excitations was analyzed,and the influence of space variable site conditions on the seismic performance of the ECSB was studied in detail.The results show that,the seismic response of the cable-stayed bridge increases gradually with the site becoming soft under the uniform site conditions.Compared with the hard site condition,the displacement of the tower top will increase 1.80 and 3.93 times respectively under the medium hard and soft site earthquake excitation.The spatial variability of ground motion caused by irregular site condition makes the seismic response of the ECSB significantly increased.Even compared with the most unfavorable situation under the uniform site conditions,the seismic response of the bridge structure under the actual site conditions is 84%greater than the response under the uniform site conditions.In the aseismic design of ECSB,the influence of space variation site conditions should be fully considered.The seismic demand of the bridge will be underestimated when the seismic performance analysis of ECSB is carried out under the uniform site conditions.