Stress Analysis And Monitoring Of Reinforced Concrete Arch Bridge With Single Rib Box During Hoisting Closed

With the increase of the span of arch bridges and the collapse of large-span bridges in the construction process in recent years,the safety of the construction of long-span bridges has been paid more and more attention.According to the Hengjiang Bridge adopts the unsupported cable single box rib hoisting and closing construction process,the construction tower is moved laterally by box ribs.Only the characteristics of single base rib closing scheme can be adopted,and the feasibility and control of single base rib closing are studied.Based on the analysis of the feasibility of single-base rib closure,four techniques for increasing the lateral stability of single-base ribs are proposed.Based on the calculation of the stability brought by various schemes,combined with the convenience of construction,The recommended scheme was also made.At the same time,the safety of the double-base ribs during the flood period was analyzed and calculated.The effects of water inflow and non-influent in the tank were considered,and the water in the tank was allowed to be allowed to reduce the adverse effects of buoyancy.In order to allow the double-base ribs to safely flood the project;in addition,the arch rib pre-camber,the arch rib stress at each stage of the bridge,the internal force and safety of the hoisting system were calculated and analyzed.Through the calculation and analysis,the following conclusions are obtained:1.For the longitudinal stability and lateral stability of single ribs,the lateral stability coefficient is 2.71<4,and measures need to be taken to meet the requirements;2.Calculated and analyzed the influence of flood on the double-base arch,and proposed that the bottom plate be treated during the prefabricated arch section so that the water can enter the arch box when the flood comes,and reduce the influence of buoyancy on the arch rib;Under the impact of flooding,the stability of the side wind cable under different initial tensions determines its initial tension.3.Four measures to increase the lateral stability of single-base ribs are proposed.Based on the calculation of the stability brought by various schemes and the convenience of construction,the scheme 2 is recommended as the implementation scheme,namely:The shore adopts 3 wind cables,and the left and right sides are symmetrically tensioned.The initial tension of the wind cables are:30kN,40kN,50kN,and the lateral stability coefficient exceeds 4,which satisfies the requirements.4.The finite element analysis method and the theoretical calculation method are used to check the force and safety of the main cable,the rear wind cable,the ventilation cable and the buckle.5.Using the flip-chip method,analyze the arch box displacement,the main cable axial force,the tower column axial force,the tower top offset during the hoisting construction process,and obtain the pre-lifting value of the arch section and the pre-bias value of the tower top;6.Referring to the existing large-span bridge construction monitoring plan and specifications,aiming at the construction characteristics of the bridge:adopting the unsupported cable single box rib hoisting and closing construction process,moving the construction tower horizontally by box rib,and proposing a targeted construction monitoring plan The construction process was monitored and the arch bridge was successfully built.7.During the construction period,the stress and displacement of the arch ribs and the line type of the arch ribs in the bridge stage were tested.The monitoring values were compared with the calculated values.The results were consistent.The bridge arch rib line type meets the design requirements.