Geometric Nonlinear Analysis Of Long-Span Steel-Box Girder Cable-Stayed Bridge

Recently, Cable-stayed bridge has been rapidly developed because of beautiful appearance, long-span capacity and convenient construction. As a kind of flexible structure with high static indetermination, compared with continuous beam and truss beam bridges, the effect of geometrical nonlinearity of cable-stayed bridge is more outstanding and the influence factors are also more, especially for long-span cable-stayed bridge. These factors mainly manifested in the following aspects:Firstly, with the increase of the length of the cable, the sag generated by self-weight of the structure increase also, at the same time, the elongation and the tension of the cable is not in proportional relation. Secondly, the geometric deformation of the whole structure is larger, performed as a notable large displacement, that is when the load in cable-stayed bridge structure effect just for a node, the node will occur displacement, the load will also move. This displacement will change the bending moment on the other node produced by the load. If the displacement amount is large, it will seriously affect the effects of the load on the structure. Coupled with the axial force and bending moment interaction effects, it will make the geometrical nonlinear of long span cable-stayed bridge analysis more and more complex. Geometric nonlinearity of cable-stayed bridge has become the important restriction factor to the development of cable-stayed bridge.The effect of geometrical nonlinearity of cable-stayed bridge includes three aspects:, cable-sage effects,combined effects of bending moment and axial force and large displacement.First, this dissertation introduces the history and development of cable-stayed bridge, and then describes the research status of the theory of geometric nonlinearity for cable-stayed bridge. Lastly, taking the2th changjiang river bridge of chongqing fengdu as research background the author did some instance. The main contents and conclusions of the research are listed as follows:Firstly, there is a introduction of the geometrical nonlinear analysis of cable-stayed bridge and its application in actual calculation, then, the author analysis the reasons and effects which caused by various nonlinear factors.(1) Based on the design scheme of the2th fengdu changjiang river, we established a finite element model to simulate the actual construction process, and then analysis the geometric nonlinearity of construction stage and completed stage.(2) Geometrical nonlinearity which affect the bending moment of the main girder, cable-sag has the most obvious effect and nonlinear of large displacement has greater effect, while the combined effect of moment and axial force has the least influence. Further, the effect degree is different in different construction phase.(3) Taking account of the temperature load, geometric nonlinear of vehicle load is obvious, so it can not be ignored.