极限边中跨比混合梁斜拉桥关键技术研究

Research on Key Technology of Compound Beam Cable-stayed Bridge with Limiting Side-Span Ratio

以主跨716 m混合梁斜拉桥为例,对结构体系、钢混结合段位置、边跨压重设计、索塔基础设计等关键技术进行研究。针对全飘浮、半飘浮两种结构体系,从主梁受力、主梁刚度、施工方案等方面进行分析研究,大桥采用全飘浮体系,既可避免大悬臂横梁设置影响美观、受力不合理等问题,又能方便钢箱梁吊装,故最终确定采用全飘浮体系。对于钢混结合段位于边跨和中跨位置的选择,从成桥状态、运营状态、支反力、施工方案等方面进行论证,考虑结合段位于中跨侧会导致主梁恒载弯矩分布不理想,同时造成边跨过重且高支架施工风险较高,最终选择边跨侧距桥塔35 m位置。针对边跨压重设计,对铁砂混凝土压重和厚板混凝土设计两种方案进行比选,考虑厚板混凝土设计结构受力满足要求,而且无须压重固定措施,简化施工工序。

Taking a compound beam cable-stayed bridge with the main span of 716 meters as an example,the key technologies such as structural system,position of steel-concrete combined section,design of side-span weight,and design of cable pylon foundation are studied.Aiming at two structural systems of full floating and half floating,the stress of the main beam,stiffness of the main beam and construction scheme are analyzed and studied.The full floating system used for the bridge can not only avoid the problems such as the influence of the large cantilever crossbeam on the appearance and unreasonable stress,but also facilitate the hoisting of the steel box girder.Therefore,the full floating system is finally adopted.The selection of the steel and concrete combined section at the side span and middle span is demonstrated from the bridge completion state,operation state,support and reaction forces,and construction scheme.Considering that the combined section at the mid-span side will lead to the unsatisfactory distribution of the constant load bending moment of the main girder,and at the same time,and cause the side span too heavy and the construction risk of high bracket high.Finally,the position 35 m from the side span side to the bridge pylon is selected.Aiming at the design of side-span weight,two schemes of iron sand concrete weight and thick plate concrete design are compared.The design structural stress considering the thick plate concrete meets the requirements,and there is no need for the weight fixing measures to simplify the construction process.