沪苏通长江公铁大桥天生港专用航道桥施工控制关键技术

Key Construction Control Techniques for Tianshenggang Special Navigation Channel Bridge of Shanghai-Suzhou-Nantong Changjiang River Rail-cum-Road Bridge

沪苏通长江公铁大桥天生港专用航道桥为(140+336+140)m刚性梁柔性拱桥,主梁为三主桁双层板桁组合结构,采用“先梁后拱,主梁双悬臂拼装,拱肋竖向转体”方案进行施工。为确保成桥线形和内力满足设计要求,采用MIDAS Civil软件建立全桥有限元模型,进行施工全过程和成桥分析,基于无应力状态法开展施工控制。钢梁墩顶节间施工时,设置墩旁托架,利用浮吊拼装;对称悬拼期间,为保证纵向稳定性,采用水袋对边跨进行配重,利用扣塔分别张拉2对扣索以改善钢梁受力并调整钢梁线形;采用预降边支点、4号墩钢梁整体预偏,以及扣索索力调整等措施进行钢梁中跨合龙;拱肋竖转后,主要通过扣索完成拱肋合龙调位;拱肋合龙后,从中间向两边张拉吊杆。经实测,该桥钢梁合龙口相对高差在10 mm以内;拱肋合龙口轴向偏差最大2 mm,相对高差最大1 mm;吊杆索力与设计目标索力偏差均在5%内,满足施工控制要求。

The Tianshenggang special navigation channel bridge of Shanghai-Suzhou-Nantong Changjiang River Rail-cum-Road Bridge is an arch bridge featuring its rigid deck and flexible arch.The bridge,with a main span of 336 m and two side spans of 140 m,accommodates two levels of decks that are supported on the three-lateral-truss main girder.The steel trusses were erected ahead of the arch,with the former erected by a two-way cantilever assembly method and the latter erected by vertical rotation method.To ensure that the geometry and internal forces of the bridge after completion could meet the design requirements,a finite element model was built up in MIDAS Civil to conduct analysis of the completed bridge and construction process and organize construction control based on stress-free method.The pier-top steel trusses were hoisted and assembled by a floating crane,with the aid of pier-side corbels.During symmetric assembly,two temporary stays were tensioned from the fastening towers to improve the load bearing condition of the steel girder and adjust the alignment of the steel girder.For the closure of the steel-truss main girder,multiple measures were taken,including pre-lowering the side supporting points,pre-offsetting the overall steel girder over pier No.4,adding water bags over the side piers and in the side spans for counterweighting to ensure longitudinal stability of the structure,and adjusting the cable forces of the temporary fastening stays.After vertical rotation of arch ribs,the fastening stays were adjusted to tune the arch ribs for closure.After the closure of the arch ribs,the suspenders were tensioned from midspan towards the two ends.The relative elevation difference of steel trusses at the closure gap was less than 10 mm.The maximum axial and elevation differences of the arch at the closure gap were 2 mm and 1 mm,respectively.The difference between the tensioning forces and design forces of the suspenders was less than 5%,meeting the construction control requirements.