大跨度外倾式拱桥稳定及极限承载力分析

摘要

为研究外倾式拱桥稳定及极限承载力问题,以九堡大桥为背景,建立有限元分析模型,分别计算了该桥线性屈曲、几何非线性稳定(分别考虑初始缺陷以及材料非线性)、弹塑性稳定状态下的稳定系数,对失稳机理以及车道荷载和静风荷载作用下的极限承载力进行分析,在此基础上讨论了荷载及横撑布置对极限承载力的影响.分析结果表明:几何非线性对于刚度较大的钢拱桥稳定的影响不大,而材料非线性对极限承载力的影响显著,弹性稳定分析会过高地估计钢拱桥的极限承载力；外倾式拱桥的失稳多为面外失稳形式,且副拱拱顶横撑对稳定的影响较小.%To study the stability and ultimate load-carrying capacity of arch bridge with out-ward inclined arch ribs, the Jiubao Bridge was cited as an example, the finite element analysis model was set up to respectively calculate the linear buckling, geometric nonlinearity stability (the initial imperfection and material nonlinearity were respectively considered) and the stability coefficients of the bridge in the state of the elasto-plastic stability and to analyze the ultimate load-carrying capacity under the action of the instability mechanism, lane load and static wind load. On the basis of the analysis, the impact of arrangement of load and cross bracings on the ul-timate load-carrying capacity was discussed. The results of the analysis demonstrate that the geo-metric nonlinearity does not have much impact on the stability of the steel arch bridge with great rigidity while the impact of the material nonlinearity on the ultimate load-carrying capacity is no-table. The analysis of the elastic stability may overestimate the ultimate load-carrying capacity of the bridge, the instability modes of the arch bridge with outward inclined arch ribs are mostly the out-of-plane instability ones and the cross bracings at the tope of the secondary arch ribs have lit-tle impact on the stability.