琅岐闽江大桥主桥钢箱梁顶推合龙控制技术

Control Techniques for Pushing Closure of Steel Box Girder of Main Bridge of Langqi Minjiang River Bridge

琅岐闽江大桥主桥为(60+90+150+680+150+90+60)m七跨连续半飘浮体系双塔双索面斜拉桥,主梁为栓焊结构钢箱梁,采用悬臂拼装法施工,中跨合龙段长12 m,合龙段自重约170 t。为了使大桥能够高精度顺利安全合龙,且成桥后结构内力、线形状态达到预期目标状态,基于无应力状态法原理的控制思想,确定中跨采用双边吊梁、无劲性骨架锁定、顶推法进行合龙。采用MIDAS Civil 2011对合龙关键工序进行详细计算分析,得到合龙顶推力、顶推位移限值等关键控制参数;分析了顶推过程中的索力、线形变化规律,以验证结构合龙安全可靠;分析得到合龙段无应力长度较小的改变对成桥目标状态影响较小。工程实践表明采用该方法进行合龙控制是可行的,桥梁合龙后内力状态与设计目标一致。

The main bridge of Langqi Minjiang River Bridge is a （60 ＋ 90 ＋ 150 ＋ 680 ＋ 150 ＋90 ＋ 60） m seven-span continuous cable-stayed bridge of half-floating system .The bridge has two pylons and the stay cables are arranged in double cable planes .The main girder adopts the steel box girders which take shape by bolting and welding and is constructed by the cantilever assemb -ling method .The closure section in the central span is 12 m long and weighs about 170 t .In order to close the bridge with high precision and ensure that the structural internal force and geometrical shape in the completed bridge state reach the target condition ,it is determined in accordance with the control principle drawn from the unstressed state method that the central span be closed by lift -ing the beams from two sides ,locking the closure gap with non-rigid skeletons and closing by pushing .The MIDAS Civil 2011 was adopted to carry out detailed calculation and analysis of the key closure operations .The key control parameters ,such as the pushing force for closure and the threshold values of pushing displacement were gained .The cable forces and the law of cable geom-etry variation during the pushing process were analyzed and the structural closure safety and relia -bility was verified .It was concluded that the minor change of the unstressed length of the closure section exerted minimal influence on the target condition of the completed bridge .The engineering practice proves that the method used for the closure control is feasible and the internal force condi-tion of the bridge after closure agrees well with the design requirements .