Study On The Effect Of Local Structure On The Performance Of The Steel Double Box Girder Bridge

As the common structure system of the steel bridge, the steel box girder bridge, the thickness of the top board, the web and the bottom plate is small, is the typical closed profiled thin-walled structure. It must set up a certain number of stiffening member like stiffening rib and diaphragm plate to ensure the stiffness and force performance to prevent instability failure. The domestic and foreign research on the effect of local structure on the performance of the steel box girder bridge is less, so this study has the extremely important practical significance regarding instructing design work.This paper applies geometry nonlinear and material nonlinear FEM Model(finite element method)to simulate and analyze the behaviors of steel double box girder bridge under uniform-loading through the calculation and analysis of19specimens of7series. The load-bearing condition of the steel double box girder bridge in a variety of situations was really simulated. The major parameters including the thickness of web, the stiffener density and the diaphragm density are studied. The main conclusions are:under uniform-loading, to the horizontal box shape the steel double box beam, the big development of the plasticity area of end beam reduces the stiffness in curve, which cause the instability. It should reinforce the support region of beam end by setting up stiffener rib or extending section of girder to transfer stress and decrease the extent of stress concentration; The mainly influence factors contains the stiffener density and the web thickness. Moreover, the effect of diaphragm density on the load-bearing capacity to steel double box girder bridge is reasonably lesser. The stiffener density’s increase can enhance strength of the steel double box girder effectively, and decrease the shear-lag effect. Based on the stress in specimens by the finite element analysis, referred to the formula of variational method, the improving formula to calculate the direct stress in section of thin-walled box girder is obtained to raise the calculation accuracy effectively.In conclusion, the FEM Model can well simulate the behavior of the steel double box girder bridge under vertical uniform-loading. The effect of various of local structure on the performance and the shear lag effect of the steel double box girder bridge is analyzed exactly in this paper. The work and the result are very serviceable for revising design specifications and guiding design of engineering. This paper will play a basic role in the further research on the linear and nonlinear structural behavior and stability of the steel double box girder bridge.