Iterative Analysis On Main Cable Shape Of Suspension Bridges With Spatial Cables

Due to the three dimensions system composed by the cable and rope of spatial-cable suspension bridge, the cross supporting capacity is increased remarkably while with small influence to vertical supporting capacity, which can raise the cross and torsion stiffness greatly.Suspension bridge is a composite system made up of the cable, the tower, stiff girder and the suspender. And the cable is the main supporting component in the system. While the analysis of the bridge structure is base on the accurate shape of the bridge, so the distribution of the whole force is influenced directly by the cable shape. In addition, the main cable shape determines its non-stress length, the location of the rope and its non-stress length, and all these parameters are indispensable in design and constructing control. In conclusion, it is very important to determine the shape of the bridge.The long-span suspension bridge is a structure with prominent nonlinear behaviors, which can be considered fully using finite element method. With the great development of computer technology, it is rational to use finite element method based on the finite displacement theory combined with universal finite element procedure ANSYS in calculating the cable shape of suspension bridge.This paper creates a three-dimension finite element model of spatial cable suspension bridge using universal finite element procedure ANSYS, and make a nonlinear static analysis, using iterative method consisting of four stages: supposition, calculation, comparison and rectifying supposition, which can get the main cable shape and the coordination of each cope satisfied with the designed shape.According to the theory and the example, it can be concluded like this: while analyzing the main cable shape of suspension bridge, it is necessary to consider the deflection of top tower saddle and the stiff arm influence of cope. In the condition of a completing bridge, the main cable shape is not at a tilted section but a spatial cable system concerned with main cable sag and side cable span.