Study On Nonlinear Static Behavior Of Siduhe River Suspension Bridge

Suspension bridge distinguishes from other kind of bridge for its unique mechanical behavior, and it is the preferabale choice for long span bridges due to its great spanning capacity. Suspension bridge is a strongly nonlinear structure while it is analyzed by a linear method in engineering caculation because of the complexity and large workload of nonlinear analysis. This thesis compares the results of nonlinear analysis in detail with that of linear analysis, based on the Siduhe Rive Suspension Bridge of Shanghai-Chengdu Expressway. Some conclusions are obtained, which are useful references for engineering practice.First, Co-rational method, a common method used in suspension bridge nonlinear analysis, is introduced in this thesis. And the algorithms of the nonlinear equations (increment method, iteration method and combination of increment and iteration method) are reviewed also.Then, construction stage analysis is performed. A planar FEM model is established with Suspension Bridge Construction Control system SBCC. The change of the system stiffness and loads in variable stages is fully considered and the movement and deformation of the saddles are taken into account. Nonlinear finite element method is employed in construction stage analysis. The shape of the main cables,the internal force and displacement of the main cables,cable pylons,hangers and stiffening girder are computed in each construction stage including the final stage. The regularity of the internal force and displacement change of the suspension bridge under vertical load is analyzed.Finally, the service stage analysis is performed. Midas/Civil,a structure analysis and optimal design system for civil structures,is used. A 3-D FEM model is established, in which the finished state of the bridge is the initial state. Effects of the three kinds of live loads (vehicle load, static wind load and temperature load) are considerd. Further more, discrepancies between the results of nonlinear analysis and that of linear analysis are discussed. It is shown that the nonlinear effects of this bridge are not so obvious, since stiffeness of the bridge becomes larger in service stage.