九江长江公路大桥塔梁临时约束设计及施工

Design and Construction of Pylon-Girder Temporary Constraint for Jiujiang Changjiang River Highway Bridge

九江长江公路大桥主桥为(70+75+84+818+233.5+124.5)m六跨不对称双塔双索面混合梁斜拉桥,南边跨及部分中跨为混凝土箱梁,其余为钢箱梁,钢箱梁采用双悬臂拼装施工工艺。为保证钢箱梁双悬臂施工期不平衡力作用下的结构及施工安全,在北塔与钢箱梁间设置了竖向、横向及纵向临时约束:通过钢绞线将设置在北塔下横梁上的竖向混凝土支墩和钢箱梁底部的钢支墩连成整体,形成竖向临时约束;竖向临时约束兼作钢箱梁双悬臂施工期间的纵向临时约束,主要由竖向临时约束产生的摩擦力抵抗在悬臂吊装过程中产生的不平衡力;在合龙阶段增设顶推装置进行纵向临时约束,兼做中跨顶推辅助合龙的顶推装置;横向临时约束主要由抗风支座和塔梁间的临时钢支墩实现。

The main bridge of the Jiujiang Changjiang River Highway Bridge is a six-span asymmetrical hybrid girder cable-stayed bridge with span arrangement of （70＋ 75 ＋ 84 ＋ 818 ＋ 233. 5 ＋ 124.5） m. It has double pylons and the stay cables are fanned out in double cable planes. The south side span and part of the intermediate span adopt concrete box girder, whereas the remaining part of the girder is the steel box girder erected by balanced cantilever assembly method. To ensure the structural stabilization and construction safety of the cantilevers of the steel box girder under unbalanced forces during the construction period, vertical, transverse and longitudinal temporary constraints were set between the north pyon and the girder. The vertical concrete supports erected on the lower cross beam and the steel supports beneath the steel box girder were connected to an integrated system by steel strands to form vertical constraint. The vertical constraint can also be used as longitudinal temporary constraint during the two-way balanced cantilever construction process, mainly using the frictional force generated from the vertical temporary constraint to resist the unbalanced force occurring during the cantilever hoisting and installing process. In the closure stage, the jacking and pushing devices were added to perform longitudinal temporary constraint, which were also used as the jacking and pushing devices that assist the closure of the intermediate span. The transverse temporary constraint was provided by wind resistant bearings and the tempo- rary steel supports between the pylon and the girder.