Study On Construction Technology Of Asymmetrical Installation Of Arch Ribs Of Long-span CFST Arch Bridge

Concrete-filled steel tube arch bridge has been developed rapidly in China because of its advantages such as beautiful shape,strong crossing ability and good economy.The majority of the long span concrete filled steel tube arch bridges are constructed by cable hoisting cantilever assembly method.According to the segments installation sequence,installations can be divided into four forms: integral assembly,frame installation,symmetrical installation and asymmetrical installation.In order to reduce the horizontal movement of the cable saddle,many large-span CFST arch bridges have been installed asymmetrically.However,few researchers do studies on construction control in this field.Therefore,this paper takes data from Guangxi Pingnan Third Bridge as the theoretical support to carry out the research on the asymmetric installation and asymmetric closure,and carries out the following work:(1)To solve the problem of the deflection of the arch ribs during the asymmetric installation while constructing the main arch ribs.Based on the influence matrix method and the principle of one tension,the Axis-Elevation Coupling Influence Matrix Optimization Algorithm is proposed to realize the each segment dual control of the vertical displacement and axis deviation.The method was applied to support engineering.The feasibility and control precision of the asymmetric installation scheme were studied by taking the number of transverse displacement of cable saddle,structural stress,cable force,overall stability,installation profile and loose cable profile as quantitative indexes.(2)In view of the error influence during the installation of the main arch ribs,based on the principle that the pre-lifting amount of the arch rib each segment of is not changed during the installation stage,the influence of geometric nonlinear effect on the bridge alignment is studied.Based on the geometric relationship in the cable-stayed buckle construction,the influential formula of the arch rib elevation is deduced while the overall temperature rises.To test the accuracy of the formula,two methods—Finite Element Analysis and Measured Linear Data are taken.(3)Aiming at the linear deviation before closing,based on the least square method and the stress-free state method,two calculation methods for adjusting the cable force before closing are proposed,which take the line shape of the closing target and the stressfree state as the control target respectively,and correct the linear deviation before closing by adjusting the minimum cable force.(4)Focusing on the stress behavior of the main arch ribs closure stage,the overall stability of the asymmetric and symmetric closure schemes in each stage is compared and analyzed.Aimed at the difficulty of linear control in asymmetric closing scheme,the matrix optimization algorithm of coupling effect of axis and elevation was applied to the construction control in the closing stage of supporting project,so as to solve the axis deviation problem caused by system transformation.