Study On Construction Control Of Cantilever Pouring Of Long-Span Reinforced Concrete Arch Bridge

The cable-stayed cantilever casting method is a construction method for concrete arch bridges,which has only been used domestic for over a decade.The cable force directly affects the internal force and line shape of the main arch ring if the arch bridge is constructed by the cable-stayed cantilever casting method.Because of the small tensile strength of concrete,the tension stress of the concrete arch ring can only be controlled by the cable force during construction to make sure the tensile stress is under control.Although the line shape of the arch ring can be achieved by the advance value,if the difference of the line shape is too large,it will definitely increase the difficulty of correcting the advance value by the hanging basket,which means it is supposed that the line shape of arch also should be under control.Based on the Jiming Three Provincial Bridge,this article systematically researches the construction control technology of the cable-stayed cantilever casting method on the main arch ring of the reinforced concrete arch bridge.The main works are as follows:(1)Aiming at the shortcomings of the stress balance method,the construction control research of the cantilever casting concrete and should be carried out under the proposing of stress and line shape double control cable force feasible domain algorithm.Select the segment point of the arch segment as the control point of vertical displacement,Proposing the displacement influence matrix about the vertical deformation of the control points of the arch segment,and introducing matrix into the linear control cable force feasible domain algorithm.In the end,combining the algorithm with the improved stress balance method to form the stress and line shape double control cable force feasible domain algorithm.Using this algorithm to theoretically analyze and accurately predict the timing of the removal of the anchor cable during the cantilever casting construction of the arch bridge.(2)Taking the Jiming Three Provincial Bridge as the engineering background,applying the stress and linear double control cable force feasible domain algorithm to the construction control of the bridge.Construction monitoring result shows that from the first section of the cantilever casting to the arch ring closure,the arch ring section stress,arch line shape,buckle tower displacement and stress controlled within a safe range,and the maximum stress of the arch ring section during construction is only 1.5 MPa,the shape of the main arch ring after closure is in good coincide with the theoretical value,the maximum deviation is only 2cm,which proves the feasibility of the cable force feasible domain algorithm with the stress and linear double control.(3)Focusing on the commonly used star-shaped and fan-shaped cable layouts at home and abroad,study the influence of the inclination of the cables under different layouts on the cable tension and the timing of removal based on the actual cable layout of the Jiming Three-Provincial Bridge,and propose the stress influence factor and displacement influence factor to quantify the timing of the demolition of the cable,make comparison and analyze the influence of different cable layouts on the stress of main arch,line shape and stability of the cable tower.