Analysis Of Ultimate Bearing Capacity Of Self-Anchored Suspension Bridges

The components of large span self-anchored suspension bridge are subjected to giant axial force and bending moment. Under the effect of combined bending and axial loading, the stability problem of self-anchored suspension bridge exists. The ultimate bearing capacity of large span self-anchored suspension bridge is necessary to be concerned in the process of design and construction, Therefore, it is necessary to analyze the the ultimate bearing capacity of self-anchored suspension bridge. The main research contents and conclusions of this thesis are as follows:Theoretical analysis method of ultimate bearing capacity of bridge was stated. The method of geometric and material nonlinearity in the analysis of ultimate bearing capacity was determined. About the geometric nonlinearity, the beam element based on CR formulation was used in this thesis to remove the contribution of the rigid body motion of the element from the total displacement field. Ernst formula which modified the elastic modulus of cable element was used to simulate the effect of cable sag effect. The Updated Lagrangian formulation was also used to establish the overall equilibrium equation of structure. About the material nonlinearity, fiber model method was considered in the material nonlinear effect. Based on the research of scanning line method and geometric characteristic calculation, the program which renewed the elastic and plastic properties of section was programmed.The incremental iterative method was chosen to solve the equilibrium equation, and the stiffness matrix singularity was also used as structural damage criterion. According to the theory of ultimate bearing capacity and the theory of finite element, the ultimate bearing capacity analysis program was developed by C++ language which was based on the Visual Studio.A spatial truss finite element model of a main span of 600 meter rail self-anchored suspension bridge was established. Meanwhile, the ultimate bearing capacity analysis of self-anchored suspension bridge was conducted by the program which was programmed in this thesis. The comprehensive verification program had certain precision by comparing with the result of ANSYS.The study of this thesis shows that the entire structure damage of self-anchored suspension bridge can be attributed to the out-of-plane failure of beam and the yield of steel sling. The structural stability safety coefficient of self-anchored rail suspension bridge in this thesis is relatively high. Even if the yield status of the steel beam section is acted as the judgment basis, the overall safety factor is also more than 1.75.