武汉二七长江大桥跨中钢梁合龙施工技术

武汉二七长江大桥主梁采用混合梁,其中汉口及武昌岸90m边跨为混凝土梁,其余梁段均为工字形截面钢-混结合梁。施工时,4号墩侧钢梁采用双悬臂对称架设,5号(3号)墩侧钢梁采用单悬臂由6号(2号)墩向跨中方向架设,跨中钢梁合龙段设置在ZL35节段。为选择有效的合龙调整措施,采用SCDS2008软件对合龙前钢梁进行敏感性分析,分析结果表明:不同的水平对拉荷载对合龙口水平位移影响较大;压重和斜拉索张拉对合龙口竖向位移影响较大;采用移动吊机调整竖向位移可控性较差。根据敏感性分析,合龙前对跨中钢梁标高及转角、纵向位移、上下游高差及轴线偏位进行调整。最终通过在5号(3号)墩布置千斤顶整体纵向移动钢梁、对孔、安装冲钉实现跨中钢梁主动合龙。

Construction Techniques for Closure of Midspan Steel Girder of Wuhan Erqi Changjiang River Bridge

The main girder of the main bridge of Wuhan Erqi Changjiang River Bridge is a hybrid girder,of which the parts of the girder for the 90-m side spans on both the Hankou and Wuchang banks are the concrete girders while the rest part of the girder is the I-steel and concrete composite girder.In the construction of the bridge,the steel girder on the sides of Pier No.4 was erected by the two-side free balanced cantilever method,the steel girder on the side of Pier No.5(Pier No.3) was erected by the one-side cantilever method,proceeding from Pier No.6(Pier No.2) towards the midspan and the closure segment of the midspan steel girder was set at Segment ZL35.To choose an effective adjustment measure for closure of the steel girder,the software SCDS2008 was used to conduct the sensitivity analysis of the steel girder before the closure and the results of the analysis showed that the influences of different horizontal pull-back loads and counterweight and stay cable tensioning respectively on the horizontal displacement and vertical displacement of the closure gap were great and the controllability of adjusting the vertical displacement,using the movable cranes,was poor.In accordance with the results of the analysis,the elevation,rotation angles,longitudinal displacement,upstream and downstream height differences and axial offsetting of the midspan steel girder were adjusted before the closure.Finally,by way of integrally and longitudinally shifting the steel girder,fitting the holes in the girder and installing the punch pins,using the jacks set on Pier No.5(Pier No.3),the active closure of the midspan steel girder was realized.