New Analytical Method For Cable System Of Suspension Bridge And Its Application

Linear and stress calculation of cable system is the key to the calculation of suspension bridges,the main calculation method contain two ways,numerical analytical method and finite element method.The numerical analytical method is a kind of calculation method that external forces under the condition of the main cable shape and internal force became understood.It can simple simulate contact problems between the main cable and saddle,with additional advantages of solutions accurately and less input data.Scholars at home and abroad has conducted a significant amount of research on the application of suspension Bridges,and put forward many practical theories.On the basis of previous work,this paper makes a detailed study on the force,structure and geometry of cablesystem,puts forward a set of improved calculation methods including main cable shape finding,saddle position calculation,saddle pre-deviation calculation and main cable cable cable adjustment calculation,and develops the relevant software.Compares and verifies the actual construction of Yangsigang Changjiang Bridge,and proves the correctness and superiority of this method.The main research contents of this paper include the following aspects:(1)The calculation process of the most widely used segmental chain line theory is analyzed in detail,with emphasis on the reasons why the equations may not be convergent.On this basis,an improved measurement method is proposed.It based on the force analysis of the main cable segment,on the basis of establishing a linear equations of the unified cable segment,find the lowest location of the main cable and its slope,established a equation based on deformation compatibility condition,then solve equations under the changing rule of the horizontal component of the main cable force,with a mechanical characteristics of clear force-bearing,strong adaptability,calculation simple and convenient.(2)Discussed the process of new method to solve the problems about main span、side span and anchor span of main cable of suspension Bridges,mainly analyzed the calculation methods of the structure asymmetry and load distribution non-uniformly(the classic segmental theory solving process may not be convergence).(3)The stress state and geometrical characteristics of the single circular curved clues saddle and composite circular curve of the saddle is worked up,and the improved calculation method about the determination of the saddle position under a state of suspension bridge is provided.Based on the geometric compatibility between the saddle and the main cable,the design position of the saddle can be obtained by solving the equation.On the basis of above,the problem of saddle correction of unstressed length of main cable is analyzed.(4)Based on the study of the mechanics and geometry of the main cable and saddle,a method for calculating the Pre-deflection of the saddle considering the coupling between the main and splay saddles is derived,and studied the application of this method in different combinations of single curve thread saddle and composite curve saddle.The method requires the solution of a ten-element nonlinear equation,so the process of solving the equations using Newton method of selecting initial values are also studied.(5)Based on the analysis of the mechanical characteristics of the main cable,two new calculating methods of the main cable tuning are proposed.First,the main idea is to extend the state equation of the main cable to Taylor and keep it to the quadratic term,the adjustment can only be obtained by solving the undivided quadratic equation for each adjustment.The second,the cable adjustment calculation based on the target state stiffness.The main idea is to calculate the stiffness of the target state by means of the segmented cable suspension,and take the stiffness as the main cable stiffness before the cable adjustment to obtain the relationship between the adjustment amount and the main cable shape.Compared with the traditional parabolic cable adjustment formula,the calculation content of the two methods is slightly increased,but the method presented in this paper is more accurate and can be operated in practice.(6)The calculation software of the cable system is compiled and applied to the design and construction of Yangsigang Changjiang Bridge.Through the practical application of the project,the feasibility of the method and software is verified.(7)An analytical method combining the analytical algorithm of saddle position with the finite element algorithm of main cable is put forward in the whole calculation process of suspension bridge.The research in this paper can provide reference method and basis for the calculation of cable system of suspension bridge.