超大型钢桁梁步履式顶推+滑块滑移施工受力分析

Analysis of Loading Conditions of Bridge Consisting of Extra-Large Steel Trusses Erected by Crawler-Type Incremental Launching System and Sliders

西安地铁10号线渭河特大桥主桥为主跨300 m的曲线上加劲连续钢桁梁桥,采用公轨合建,双层桥面布置,上部结构采用超大型钢桁梁与曲线加劲弦组合结构。主桥施工时先架设钢桁梁,再施工刚性加劲弦。钢桁梁采用步履式顶推+滑块滑移施工,顶推采用南、北双向同步施工。为保证顶推施工过程中主体结构及临时支撑结构的受力安全,采用MIDAS Gen软件建立主桥有限元模型,采用生死单元法进行施工全过程分析,对钢桁梁承载力、支座反力、合龙阶段落梁变形调整值、合龙阶段温度效应影响、顶推过程中不同步的影响以及瞬时阵风作用下顶推体系承载力进行分析验算。结果表明:钢桁梁的承载力及瞬时阵风作用下顶推体系承载力均满足规范要求;钢桁梁顶推时墩顶最大支座反力取值24000 kN;南侧W05墩与北侧L08临时墩落梁变形调整值分别取-60 mm和-40 mm,以消除合龙口端部下挠变形;以环境温度20℃为参考值,整体升温不超过10℃和上、下弦温度梯度为10℃以内时对合龙影响不大;顶推过程中横、纵向瞬时不同步位移建议分别控制在5 mm和20 mm以内。

The main bridge of Weihe River Bridge carrying a section of the Xi′an Metro Line 10 is a bridge with superstructure consisting of extra-large steel trusses,stiffened by two continuous spans of upper arch chords and inclined rigid suspenders.The bridge has two levels of decks accommodating road and light rail traffic,respectively.During the construction,the steel trusses were erected ahead of the stiffening upper arch chords.The steel trusses were erected by a crawler-type incremental launching system from the north and south banks towards the center,assisted by sliders.The construction process of the full bridge was numerically simulated in MIDAS Gen to ensure the loading safety of the main bridge structure and the temporary supporting structures by activating and deactivating elements during analysis.Multiple factors were analyzed and checked,including the load bearing behaviors of steel trusses,reaction forces of bearings,truss lowering deformation adjustment at closing stage,thermal effects at closing stage,asymmetry in incremental launching,and the loading bearing capacity of the incremental launching system under gusts.It is shown that the load bearing capacity of the steel truss girder bridge and the load bearing capacity of the incremental launching system met the code requirements.The maximum reaction force of bearings at each pier was 24000 kN.The truss lowering deformation adjusting values for the south W05 pier and the north L08 temporary pier were-60 mm and-40 mm,respectively,aiming to eradicate the down warping of tips of cantilevers at the closure gap.The closing of the superstructure would not be hindered,as the integral temperature rise is less than 10℃,considering a reference ambient temperature at 20℃,and the temperature gradients of the upper and lower chords are within 10℃.The transverse and longitudinal instantaneous asymmetric displacements during incremental launching were controlled within the ranges of 5 mm and 20 mm,respectively.