Research On Cable Force Calculation Method Of Cable-Stayed Fastening Hanging Methods Of Long Span Concrete Filled Steel Tube Arch Bridge

Cable-stayed fastening-hanging cantilever assembly methods are widely used to construct concrete-filled steel tube(CFST)arch bridges.The number of arch rib segments continued to increase with the increase of the span of the CFST arch bridge,the one-time tensioning method was usually adopted to avoid the repeated adjustments of cable force during the construction process,cable forces are the key to control the arch rib alignment and the results of cable forces were affected by many factors during the calculation process.It is a topical issue that calculates a group of cable forces to make the arch rib alignment reach the expected target in the construction calculation of the CFST arch bridge efficiently and accurately.Therefore,it is necessary to study the influenced factors during the cable force calculation process.The purpose of this study was to analyze the calculation of cable-stayed fastening-hanging methods for the Third Pingnan Bridge(575m half through CFST arch bridge),as follows:(1)The influence matrix method based on the forward iteration method was studied,the calculation principles and steps in the influence matrix method and forward iteration method were expounded.The feasibility and accuracy of the influence matrix method in cable force calculation of the cable-stayed fastening-hanging method were verified through a calculation example.The low convergence efficiency in the cable force calculation in the influence matrix method was pointed out based on the study of the influenced factors in convergence efficiency.The correction matrix of the influence matrix was derived through theoretical analysis,and an improved iterative algorithm was proposed.The results show that the convergence efficiency of the improved iterative algorithm was improved by 65%.(2)Based on the finite element model of the Third Pingnan Bridge,the influenced factors of calculated value in cable force calculation of cable-stayed fastening-hanging method were studied.Pre elevation of segment installation,arch rib alignment during the construction process,arch rib alignment,and arch rib stress after cable loosening were considered to analyze the difference between the value calculated by Optimal Cable Loosening Alignment Methods and Optimal Construction Alignment Methods.The result shows that the cable force calculated by Optimal Construction Alignment Methods can effectively reduce the linear fluctuation of arch rib alignment during the construction process,the initial stress of arch rib after cable loosening can be effectively reduced by controlling the arch rib alignment during the construction process.(3)The Optimization Algorithm Method that applies to the cable-stayed fastening-hanging method of the long-span CFST arch bridge was proposed.The cable forces that calculated by the simplified moment balance method were used as the iterative initial value.The displacement of control points and the maximum cable forces of adjacent cables during the construction process were constrained,the objective function was the minimum adjustment range of cable force.As an example,the cable force of the Third Pingnan Bridge was calculated by The Optimization Algorithm Method.The result shows that the difference between the calculated arch rib alignment and the target arch rib alignment was less than 30 mm,the maximum fluctuation of the control point was only 139.4mm,the maximum difference of stress was 25.58 MPa compared to One-Step Forming.