蒙华铁路洞庭湖特大桥主桥钢梁架设关键技术

蒙华铁路洞庭湖特大桥主桥为主跨406m的三塔斜拉桥,主梁采用钢箱-钢桁组合结构。其中,下部钢箱梁宽21m,中心处梁高2.5m;上部钢桁梁采用华伦式布置,节间长14m,桁高12m。该桥主梁采用"先箱后桁"的方案施工,先安装下部钢箱梁,钢箱梁合龙后,在其顶面分组安装钢桁梁。边跨钢箱梁采用顶推法架设;主跨钢箱梁采用悬臂拼装法架设,钢箱梁节段利用300t架梁吊机整体吊装,在主跨跨中采用主动合龙方式合龙。上部钢桁梁杆件采用上弦杆制造长度修正、分组架设(5个节间为1组)、多个调整口合龙等技术施工,完成钢桁梁杆件拼装,并实现精确合龙。

Key Techniques for Erection of Steel Girder of Main Bridge of Dongting Lake Bridge on Mengxi-Huazhong Railway

The main bridge of the Dongting Lake Bridge on Mengxi-Huazhong Railway is a three-pylon cable-stayed bridge with the main span of 406 m, and the steel box-steel truss composite structure is adopted for the main girder. The width of the lower steel box girder is 21 m and the height of the steel box girder at bridge centerline is 2.5 m;the upper steel truss girders are arranged in the Warren style, in which the length of inter node is 14 m, and the height of truss is 12 m. The construction method of " firstly erecting steel box girder and then steel truss girder " is used in the erection of main bridge. The lower steel box girders are erected firstly, then the steel truss girders are erected on the top of steel box girders after the closure of steel box girders. The method of incremental launching is used for the steel box girder of the side span. The steel box girders of the main span, which are integrally hoisted by the 300 t girder crane, are constructed by the cantilever installation method. The main span is closed by active closure measures. Construction measures, including length correction of upper chord manufacturing, erection of steel truss girder in groups(5 panels for 1 group), and closure of multiple adjusting joints, are taken for the upper steel truss girders to complete the erection of the steel truss girders, then the objective of closure in high-precision is achieved.