| CFST arch bridges have been rapidly developed in China because of their advantages such as high strength,good ductility,impact resistance,and the use of empty steel tubes as template during core concrete construction.So far,the vast majority of CFST arch bridges in China have been constructed by cantilever assembly method.However,with the increasing span of the arch bridge,the corresponding number of lifting segments also increased.Due to the influence of manufacturing accuracy,cable force error,temperature effect,and measurement error,the actual measured deformation of the arch ribs inevitably deviates from the theoretical value.If the control and adjustment are not carried out,the error will accumulate gradually,causing the deviation of the arch rib alignment and even the difficulty of arch rib closing.Therefore,the importance of realtime alignment control and error analysis is highlighted.In this dissertation,the following research work is carried out based on the project of Qianwei Minjiang River Bridge(main span of 458m)in Sichuan Province :(1)In view of the problems of the traditional cable force optimization method with many constraints,complicated solutions,and large fluctuations in the optimized cable force value and construction pre-lift value,the "cable force optimization method based on influence matrix" is applied in the calculation of cable force relying on the project,and further in the optimization algorithm,the displacement influence matrix of the pre-lift amount of the arch rib is introduced to realize the dual control of the alignment of the arch rib during the lifting stage and after removing the cable.(2)Based on the sources and types of errors in the construction of steel tube arches,the effects of the length errors of the arch ribs,the installation errors at the sealing stage,the deviation of the tower and the temperature errors on the arch rib alignment and stress are analyzed,and the theoretical formula of the above corresponding errors on arch rib alignment is derived;The influence of inserting steel plate between arch segments on arch rib alignment is studied,the process of inserting steel plate is simulated by the coordinate modification,and the order flows about the simulation analysis is programmed based on ANSYS software.(3)The sensitivity analysis of the main design parameters in the process of steel pipe arch lifting is carried out,and the application of the least square method in single parameter estimation and multi-parameter mixed estimation is discussed;for the parameters that can be identified directly in error control,the corresponding adjustment strategy is proposed;and in view of the control error caused by the deviation of arch rib manufacturing length and the offset of the measuring point,a control method for dynamically correcting the pre-elevation of the true position of the measuring point by geometric analysis is proposed,and this method is applied to the construction control of Minjiang Bridge in Sichuan Province.(4)In view of the unavoidable installation errors during the installation of steel tube arches,a real-time control method for the arch rib alignment errors based on the influence matrix and the least square method is proposed.The relationship between the force adjustment volume and the construction prelift value and arch displacement is established by using the influence matrix,the displacement results after the cable force adjustment can be directly obtained as the basis for construction control;Furthermore,the "feasible region" control method of pre-elevation control is proposed to realize the real-time discrimination of reasonable alignment of arch rib.(5)In view of the problem of secondary cable adjustment that may occur before arch rib closing,a cable adjustment method with the least amount of cable adjustment is applied,which solves the problem of excessive amount of cable adjustment in the traditional method.Finally,combined with the theory of gray system,the research of the prediction mechanism of the cable force in the process of arch rib installation is carried out. |
