Carrying Capacity Analysis Of Open-Web Space Truss Pedestrian Bridge

With the rapid development of Urban Transportation Infrastructure and high-way in our country recently, the pedestrian bridges for span the road were constructed abundantly. As the traditional Reinforced Concrete Bridge is a hindrance to the view, the span is limited,and the consumption of steel material of Box Beam Structure is too large,it is exigent to develop a new Structure of pedestrian bridges. This structure should be harmonize with the modern city. Achieve all kind of plane ,vertical and section structure pattern and should be economical,beautiful. Open-Web Space Truss Pedestrian Bridge can meet demands mentioned above,and has been used in the engineering.In recent years, Grid structure collapse accidents often occurs there are no significant premonition before structure failure,so it is necessary to analyze the carrying Capacity of this structure. This paper applies Ansys to analyze the carrying capacity of Open-Web Space Truss Pedestrian Bridge. The contents of this dissertation are: 1 .Analyse the strength and stiffness of finished bridge state. 2.Tracing analyze the structure state in four Condition. Generating "Factor-δ"curve by considering residual Stress and nonlinearity to ascertain the ultimate carrying capacity of the structure. 3.Analyze the effect of Wind load to the ultimate carrying capacity. 4.Some typical spherical nodes were analyzed. It was shown that the spherical node should not failure than the bar component. Based on above analysis, some conclusions were drawn as following.(1) Domino effect caused by unstability of the main compression bar can result in the collapse of the grid,and the collapse is abrupt.(2) Generally,the compression bar of the grid, especially the unstable failure of compression web bars in a three-layer space truss will terminate the icrease of grid's carrying capacity and the yielding of tension bar will not effect this kind of carrying capacity. Compression bar collapse result very serious internal force redistribution in the neighboring region .(3) Using the weak tension bar and strong compression bar consciously in design, let the tension bar collapse first and make this trend had certain extent of continuity, this can keep the plasticity of grid to develop, and effectively raise the ultimate carrying capacity.(4) Bolt-sphere joints in where the ball and bolt or sleeve contact will occur the phenomenon of stress concentration. It requires special attention and takes appropriate measures to prevent the spherical joint collapse before the bar, consequently reduce the carrying capacity of the structure.