罕遇地震下大跨张弦桁架结构地震反应分析

SEISMIC RESPONSE ANALYSIS OF LONG-SPAN TRUSS STRING STRUCTURE UNDER RARE EARTHQUAKE

为了研究大跨张弦桁架结构在罕遇地震下的抗震性能和地震反应规律,采用STCAD软件建立结构有限元模型再导入SAP 2000中分别进行多维单点和多维多点的地震时程分析,依据工程实际选取三种视波速来考虑行波效应的影响。最终从构件的应力、工作状态及内力时程三个方面对多点和一致输入的计算结果进行了对比分析。结果表明:大跨张弦桁架结构在罕遇地震下的抗震性能良好,但结构存在薄弱部位;多点输入对结构上部桁架和山墙的影响很大,而对索和撑杆的影响较小。建议大跨张弦桁架结构在罕遇地震下的抗震验算应考虑多维多点输入,并选取不同视波速进行验算,取最不利视波速的结果作为参考。

In order to study the seismic behavior and the seismic response properties of long-span truss string structure under rare earthquake,the structural finite element model was established by using the software STCAD.And then the seismic time-history analyses under uniform support excitations and multi-support excitations were performed respectively after importing the model into FEM software SAP 2000.The travelling wave effect was considered by selecting three different apparent wave velocities according to the fact of project.The results were compared between multi-support and uniform support excitations from three aspects:element stresses,element working status and internal force time history of the element.The results indicated:long-span truss string structure had good seismic behavior but existed unsubstantial part;Multi-support exitation had a great influence on the upper truss and gables,but had a less influence on cables and struts.Therefore,multi-dimension and multi-support excitations were suggested to be considered in seismic checking under rare earthquake for these structures,and different apparent wave velocities should be selected so as to find the most unfavorable one for reference.