铁路大跨度钢管混凝土拱桥弹性稳定性分析

以银吴(银川—吴忠)铁路银川南特大桥128 m钢管混凝土系杆拱桥为背景,建立空间有限元模型,分析了恒载及恒载+最不利活载2种荷载工况下该桥的稳定安全系数及失稳模态。着重分析了拱肋横撑形式、矢跨比、吊杆非保向力对稳定性的影响。研究结果表明:结构的失稳主要为拱肋面外失稳,满足稳定安全系数大于4~5的要求,且活载对全桥稳定性的影响远小于自重和二期恒载的影响。采用K形横撑时稳定安全系数相较于I形横撑提高了198%,对稳定性提高最为明显,采用米字形横撑稳定性最好,因此,在选择横撑形式时优先考虑米字形横撑和K形横撑。矢跨比从1/7增大至1/3时,稳定安全系数呈先增大后减小的趋势,在1/5~1/4时达到峰值,1/4.5时最大;吊杆非保向力对拱桥稳定性有一定影响,吊杆将拱肋与系梁连接成整体可以提高拱桥整体稳定性。

Elastic Stability Analysis of Railway Long Span CFST Arch Bridge

Taking a 128 m concrete-filled steel tubular arch bridge of Yinchuan South Bridge on Yinchuan-Wuzhongrailway as the background,the spatial finite element model was established to analyze the stability safety coefficient andinstability modes of the bridge under the dead load and the dead load+the most unfavorable live load.The influence ofarch rib bracing form,rise-span ratio and non-directional force of suspender on stability was analyzed emphatically.Theresults show that the instability of the structure is mainly out of plane instability of arch rib,which meets therequirement of stability safety coefficient greater than 4~5,and the influence of live load on the stability of the wholebridge is far less than that of dead weight and second stage dead load.The stability safety coefficient of K-shaped braceis 198%higher than that of I-shaped brace,and the most obvious improvement is in stability.The stability of the crossbrace with cross-shaped is the best.Therefore,the cross-shaped and K-shaped braces are preferred in the selection ofcross braces.When the rise-span ratio increases from 1/7 to 1/3,the stability safety coefficient increases first and thendecreases,reaching its peak value at 1/5~1/4 and maximum at 1/4.5.The non-directional force of suspender has acertain influence on the stability of arch bridge.The suspender connecting arch ribs and tied beams as a whole structurecan improve the overall stability of arch bridge.