Analysis Of The Overall Stability For The Large-span Concrete Cable-stayed Bridge

With the increment of span of modern cable-stayed bridges, towers become more and more high. The axial compressive forces in the tower and girder greatly increase while the sag effect, geometric and material nonlinearity of cables also become pronounced. These negative effects would greatly reduce the stability of cable-stayed bridges. The stability of cable-stayed bridges becomes an important problem. The first and second stability problems of cable-stayed bridges with long span are investigated by application of finite element method in this work. At the same time, the stability evaluation index and the corresponding criterion are discussed. The problem of establishing FEM model is studied. The elastic buckling analysis and nonlinear buckling analysis of a cable-stayed bridge are made by using the ANSYS commercial software.The elastic stability and nonlinear stability analyses are performed for Yibin Yangtze River Bridge by using the spatial finite element method. The global stability of this bridge is assessed according to the FEM result. By taking the geometric nonlinear effect into account, the stability safe factor slightly decreases. However, when the both geometric and material nonlinearities are considered, the stability safe factor would greatly decrease. This implies that the material nonlinearity has a large influence on the stability of cable-stayed bridges. Moreover, the influences of structural parameters on the elastic stability are discussed. The influences of cable sag effect, girder-tower effect and large displacement effect on the geometric nonlinear stability are also studied. The different loading modes in the static stability analysis for the large-span cable-stayed bridges are compared. The results can be taken as a reference for the design and construction of the cable-stayed bridges.