大跨四线铁路上承式钢桁拱桥拱上梁设计

大瑞铁路保山至瑞丽段采用跨度490m的上承式钢桁拱桥跨越怒江,该桥为高烈度地震区大跨度四线铁路桥,在桥上设站。对拱上梁的跨径、联孔、梁型和支座设置进行比选,确定拱上梁采用一联14×37.2m钢箱梁,拱上立柱采用钢结构双柱排架墩,钢箱梁与拱上立柱之间设置纵向固定支座以提高墩的纵向刚度。桥面总宽度为24.9m,分双幅对称设计,单幅钢箱梁采用双箱单室大悬臂结构。采用MIDAS Civil软件建立拱上钢箱梁局部空间板壳有限元模型进行结构分析,结果表明:大悬臂钢箱梁横向偏载效应较为明显,各支点反力由外向内依次减小,最不利状态下最小抗倾覆系数满足设计要求;钢箱梁应力、位移及疲劳验算均满足规范要求。

Deck Design for a Deck-Type Long-Span Steel Truss Arch Bridge Carrying Four Railway Tracks

The Baoshan-to-Ruili section of Dali-Ruili Railway has a deck-type steel truss arch bridge crossing the Nujiang River.The railway bridge with an arch spanning 490 mis located in seismic region with high intensity,and accommodates four railway tracks and a railway station.The span lengths,configuration of continuous units,deck type and layout of bearings were studied.A steel box girder deck with a continuous unit of 14×37.2 m was finally chosen.The spandrel consists of steel bents each with two columns,between the steel box girder and the spandrel,longitudinally-fixed bearings are installed to improve the longitudinal stiffness of the bents.The deck has a total width of 24.9 m,consisting of symmetrical left and right halves,of which,each half contains double single-cell box girders with large cantilevers.The software MIDAS Civil was used to establish the local spatial plate and shell element model of the steel box girders for the structural analysis.The results demonstrate that the transverse eccentric loading effect of the large-cantilevered steel box girder is significant,the reaction forces show the sign of gradual decrease from the outer supports to the inner ones,and under the most unfavorable loading condition,the minimum anti-overturning coefficient can meet the design requirements.The stresses and displacement of the steel box girder as well as fatigue verification can also satisfy the code requirements.