Research On Construction Scheme For Superstructure And Its Stability Of Super Steel Truss Girder Cable-stayed Bridge In The Mountainous Area

With the comprehensive implementation of China's western development strategy and the new requirements for infrastructure in mountainous areas,the construction of large-span Bridges in mountainous areas is growing.The steel truss girder cable-stayed bridge not only conforms to the development trend of steel bridge in China,but also adapts to the conditions of transportation and installation in mountainous area.It has the characteristics of large span ability,light and beautiful structure,high economy,good durability,green environmental protection and so on.Based on this,taking the Zhongjian River super steel truss girder cable-stayed bridge of the En Lai En Qian highway in Hubei province as an example,the construction scheme for superstructure and its stability of super steel truss girder cable-stayed bridge in mountainous area are systematically studied using the method of numerical analysis and theoretical analysis.The research results provide strong technical support for bridge construction,and provide valuable reference for the design and construction of similar bridges.The main conclusions are as follows:(1)From the aspects of structural construction safety,large temporary structure quantity,construction period,construction feasibility and advantages and disadvantages,the most suitable construction scheme for superstructure of Zhongjian River super steel truss girder cable-stayed bridge is determined.(2)Based on the numerical analysis method,the static wind stability and wind-induced vibration response of the structure under the most unfavorable conditions in the construction process are analyzed.The results show that there will be no static wind torsional instability and no danger of galloping in the main girder during the construction period of Zhonghe River Bridge.In the range of-5° to +5° wind attack angle,the critical flutter velocity of the main girder in construction stage is higher than that of the corresponding flutter test wind speed,and its flutter stability meets the design requirements.(3)Under the design wind speed in the construction stage,the wind-induced buffeting displacement of the main girder decreases after the anti-wind cable is connected to the earth.Under the condition that the tensile elongation of the anti-wind cable is constant,the greater the area of the anti-wind cable is,the more obvious the inhibition effect on the buffeting displacement is.(4)Combined with the theory of structural stability calculation,the stability of the first type and the second type of the structure under the critical conditions such as the maximum double cantilever,the maximum single cantilever and the bridge completion stage during the construction period are studied.The analysis shows that the stability of the construction stage is safe.At the same time,the lane load in the operation stage has little effect on the stability safety factor of the structure,that is,the structural stability of the operation stage is also safe.(5)The calculated results of structural theory show that the safety factor of nonlinear stability of structure is much smaller than that of elastic stability.In the calculation of stability of long-span steel truss girder cable-stayed bridge,the influence of non-linear factors on the safety factor of structural stability is large.