独塔非对称钢-混混合梁斜拉桥抗震性能研究

Seismic performance of single-tower cable-stayed bridge with asymmetric steel-concrete hybrid girder

【目的】研究独塔非对称钢-混混合梁斜拉桥的抗震性能,并探明非对称结构地震响应的差异。【方法】以长沙香炉洲大桥西汊航道桥为依托,采用MidasCivil软件建立非对称钢-混混合梁斜拉桥全桥有限元模型,分别采用反应谱法和非线性时程分析法对其进行地震响应分析,并重点研究了结构非对称性对斜拉桥辅助墩、过渡墩及其桩基抗震性能的影响。【结果】独塔非对称钢-混混合梁斜拉桥的动力特性和地震响应规律呈现出明显的非对称性,非对称布置的两过渡墩和两辅助墩在地震作用下的内力响应存在较大差异,结构的非对称性对横向地震更加敏感,在抗震设计时应予以重视;除两过渡墩桩基外,长沙香炉洲大桥按照静力计算设计的结构尺寸及配筋形式均能满足各工况地震作用下的抗震性能目标;塔身、墩身在横向+竖向地震作用下的安全储备均大于纵向+竖向地震的,桩基在横向+竖向地震作用下的安全储备几乎都小于纵向+竖向地震的;受结构非对称性的影响,边跨的27#过渡墩桩基总是先于主跨的31#过渡墩桩基发生破坏;在横向地震作用下,受群桩承台影响横向各排桩基地震轴力有较大差异。【结论】从经济性和抗震合理性角度出发,应对独塔非对称钢-混混合梁斜拉桥进行差异化的抗震设计,研究成果可为非对称斜拉桥及其他非对称桥梁结构的抗震设计提供有益参考。

[Purposes]This paper aims to study the seismic performance of single-tower cable-stayed bridges with asymmetric steel-concrete hybrid girders and explore the differences in seismic response of asymmetric structures.[Methods]Midas Civil software was used to establish a finite element model of the entire cable-stayed bridge with asymmetric steel-concrete hybrid girders based on the West Branch Channel Bridge of Changsha Xiangluzhou Bridge.The seismic response analysis was conducted using the response spectrum method and the nonlinear time history analysis method,respectively.The impact of structural asymmetry on the seismic performance of auxiliary piers,transition piers,and pile foundations of the cable-stayed bridge was mainly studied.[Findings]The dynamic characteristics and seismic response of the single-tower cable-stayed bridge with asymmetric steel-concrete hybrid girders exhibit significant asymmetry.There are significant differences in the internal force response of the two transition piers and two auxiliary piers arranged asymmetrically under seismic action.The structural asymmetry is more sensitive to lateral earthquakes and should be taken seriously in seismic design.Except for the pile foundations of the two transition piers,the structural dimensions and reinforcement forms of Changsha Xiangluzhou Bridge designed according to static calculation can meet the seismic performance goals under various earthquake conditions.The safety reserves of tower and pier bodies under lateral and vertical seismic actions are greater than those under longitudinal and vertical seismic actions,while the safety reserves of pile foundations under lateral and vertical seismic actions are almost all smaller than those under longitudinal and vertical seismic actions.Due to the influence of structural asymmetry,the pile foundation of the 27#transition pier of the side span always fails before that of the 31#transition pier of the main span.Under lateral seismic action,there are significant differences in the seismic axial force of each row of pile foundations affected by the bearing platform.[Conclusions]From the perspective of economy and seismic rationality,differentiated seismic design should be carried out for single-tower cable-stayed bridges with asymmetric steel-concrete hybrid girders.The research results can provide a useful reference for the seismic design of asymmetric cable-stayed bridges and other asymmetric bridge structures.