成贵铁路鸭池河特大桥主梁大节段整体吊架现浇施工控制技术

Construction Control Techniques for Large Girder Segments Cast in Situ Using Integral Suspended Scaffolds of Yachi River Bridge of Chengdu-Guiyang Railway

成贵铁路鸭池河特大桥主桥为中承式提篮拱桥,拱上主梁为跨径(32+272+32)m的单箱三室预应力混凝土结构,边跨及中跨无吊杆区主梁采用在拱上搭设支架整体现浇,中跨吊杆区主梁采用整体吊架体系分节段浇筑。为了保证成桥后主梁线形和吊杆索力满足设计要求,采用MIDAS Civil软件建立主梁施工阶段有限元模型,利用正装计算分析法和实时监测的手段进行施工控制。在施工控制过程中,对中跨吊杆区整体吊架体系施工的主梁采取一次性总体预拱度设置,对吊杆采取两阶段张拉控制,减少了主梁分阶段立模次数,避免了主梁节段浇筑过程中对吊杆索力的频繁张拉调整,过程控制线形、索力目标明确,结构状态清晰,控制方便。成桥后对主梁高程、吊杆索力的实测值与理论值进行对比分析,结果表明:主梁高程、吊杆索力的实测值与理论值吻合较好,误差在合理范围内,满足设计要求。

The main bridge of Yachi River Bridge of the newly-built Chengdu-Guiyang Railway is a half-through basket-handle arch bridge.The deck consists of three spans of three-cell prestressed concrete box girders,with span lengths of 32,272 and 32 m.The girders in the side spans and the hanger-free zone of the central span were cast in place using the arch-carried scaffolds,while the girders in suspension zone of the central span were cast in segments using integral hanger-suspended scaffolds.To ensure that the deck alignment and hanger forces could meet the design requirements after the completion of the bridge,numerical simulation of the deck construction was conducted using MIDAS Civil,and forward calculation and live monitoring were performed to control the construction process.During construction control,the girders in the suspension zone of the central span that were cast using the hanger-suspended scaffolds were pre-cambered once as an entirety,and the hangers were tensioned in two phases,with intent to reduce the cycles of scaffolds installation and demolition and avoid the frequent tensioning and adjusting of hanger forces during the girder casting.The targets of deck alignment and hanger force control were clear,the conditions of the structure in different construction stages were under control,and the whole construction control process was eased.After the completion of the bridge,the calculated and theoretical deck elevation and hanger forces were compared,and the results indicated that the two were in good agreement,the bias was within reasonable range and met the design requirements.