Cable Force Test And Optimization Study Of Long-span Decorative Steel Box Arch Suspender

With the improvement of national economic level,people have higher and higher aesthetic requirements for bridges.Arch bridges,cable-stayed bridges and suspension bridges have been designed and constructed on a large scale.These bridge forms have important stress components,namely suspender,so the test of suspender cable force and the optimization of cable force are of great significance.The main research of this paper is as follows :1.Review the research status of vibration frequency method and cable forceoptimization.The linear vibration theory of cables and the analytical theory for solving the cable force are summarized.According to the structure and layout of the real suspender,a practical formula for calculating the cable force considering the influence of the anchorage at the homogeneous end of the cable is introduced.2.According to the characteristics of the real cable : cable with anchors at both ends and non-homogeneous anchor at one end and homogeneous anchor at the other end,a theoretical model of ’ non-homogeneous end ’ cable closer to the real structure of the cable is proposed.Through the finite element method,the influence of the change of three parameters characterizing the ’ non-homogeneous ’characteristics on the results of the cable force calculation formula considering the influence of homogeneous end properties is studied,and the influence law of various parameters on the influence coefficient of proportional variables is summarized.The results show that it is sensitive to the short suspender,and the cable force calculation of the short suspender should consider the further correction of the influence of the heterogeneous end properties.At the same time,aiming at the problem of bending stiffness identification of cables,a bending stiffness identification method is proposed,which only needs to measure the multi-order natural vibration frequency of cables without considering the influence of bonding between steel strands and HDPE.3.Combined with the actual project of Yuji Bridge,the engineering background and finite element model are introduced.At the same time,the measured process of cable frequency in this project is introduced.The measured cable frequency data are substituted into the existing analytical formula and the practical formula considering the homogeneous end characteristics,as well as the cable force calculation considering the influence of the ’ non-homogeneous end’ characteristics.The results of three groups of cable force calculation are compared with the results of finite element calculation.It is concluded that when calculating the cable force of the cable with anchors at both ends,the influence of the end properties of the cable can be accurately considered to ensure the accuracy of the results.At the same time,it is also proved that the non-homogeneous nature of the end is sensitive to the calculation results of the short suspender.4.The method for determining the target cable force of finished bridge is studied.The double optimization method of influence matrix is applied to continue optimizing the cable force target with the minimum bending energy method as the initial value,and the target cable force of finished bridge with small bending strain energy and uniform cable force can be obtained.According to the target cable force value,the influence matrix method is used to obtain the adjustment scheme with the cable force value as the control variable.The optimized data results are finally reduced from the initial maximum error absolute value of 44.33 % to1.38 %,which proves the effect of the influence matrix method on the adjustment and optimization of the cable force value of the suspender.Combined with the actual cable structure of this project,the lower end of the suspender can control the suspender length by screw,so how to use the stress-free state control method based on the influence matrix method to adjust the cable force is studied,and the adjustment scheme with the stress-free length of the suspender as the control variable is obtained,which can better adapt to the influence of tension sequence,temperature change and other factors on cable adjustment,and has certain practical significance for practical engineering.