赤水河红军大桥门式框架桥塔施工关键技术

赤水河红军大桥为主跨1200 m的单跨悬索桥,桥塔为门式框架结构,由塔肢和上、下2道横梁组成。为加快施工进度,对塔梁同步和塔梁异步2种施工方案进行综合比选,确定该桥采用塔梁异步施工方案。通过方案优化,施工中设置5道主动横撑,确保桥塔不出现拉应力;横梁采用空中附壁支架现浇施工,节省钢材,缩短工期;采用有限元软件对该方案进行仿真分析,验证了该方案的合理性。塔梁异步施工时,塔肢施工到一定高度后进行下横梁施工;塔肢封顶后,同步施工大桥上部结构和上横梁;通过横梁与塔肢结合处钢筋全断面Ⅰ级接头控制,增加塔肢混凝土凿毛厚度,采用定位钢筋串联法进行横梁锚杯相对位置及线形控制,预应力管道口采用定位钢筋进行位置固定,保证了桥塔施工质量。

Key Construction Techniques for Portal-Frame Towers of Chishui River Red Army Bridge

The Chishui River Red Army Bridge is a single-span suspension bridge with a main span of 1200 m.The tower is a portal-frame structure,comprised of tower legs and the upper and lower cross beams.To accelerate the construction,the two schemes of parallel tower and girder construction and separate tower and girder construction were comprehensively compared,and the separate tower and girder construction was finally chosen.After scheme optimization,a number of 5 active cross beams were installed to make sure that there would not be tensile stress in the tower.The cross beam was cast in situ by using the overhead wall-attached scaffoldings,with the intention of saving steel and shortening the construction time.The scheme was verified reasonable by the finite element analysis.During the separate tower and girder construction,the erection of the lower cross beam started only when the tower columns rose to a certain height.When the construction of the tower columns were completed,the superstructure of the bridge and the upper tower cross beam were simultaneously constructed.A variety of measures were taken to ensure the construction quality of the towers,for example,I-grade joints of reinforcement in the full cross section at the connecting part of the cross beam and tower columns were used for control,the roughened thickness of the concrete in the tower columns was increased,the positioning reinforcing bars were in series connection to control the relative location and alignment of the anchor sockets in the cross beams,and positioning reinforcing bars were added at the openings of the prestressing ducts to fix the location.