Nonlinear Analysis On Aerostatic Stability For Long Span Suspention Bridge

With the span of bridges becoming longer and longer, the static and dynamic problems of the bridge structure induced by wind are more and more serious. According to the results of the wind tunnel model tests home and abroad, the critical wind speed of the aerostatic stability of long-span bridge may be less than that of the aerodynamic stability. In addition, the effects of geometric nonlinearity and the static wind load nonlinearity of long-span bridges under strong wind load shouldn't be neglected. Therefore, the research about the problems of the aerostatic stability of long-span bridges, particularly the suspension bridges, is an important direction.On the basis of the project The Fourth Bridge Of Nanjing Yangtze River, using the MARC FEM software,the aerostatic stability of this suspension bridge was studied in this paper. First, considering the effects of geometric nonlinearity and the wind load nonlinearity, the controlling program was developed by combining the static wind load increment and the double iteration procedure in analyzing the aerostatic stability of the long-span suspension bridge, and the whole procession of aerostatic instability of this long-span suspension bridge was analyzed and thus the critical wind speed of the aerostatic stability was obtained by using this procedure, also revealed the laws of aerostatic instability. Then, the influences of the wind load of main cable or the suspender on the aerostatic stability were studied by calculating, and the aerostatic stability of the suspension bridge with different initial attack angles was analyzed with the linear method and the nonlinear method. Last, linear method and nonlinear finite element method of the aerostatic stability were detailedly compared in this thesis. It was shown that it will overrate the aerostatic carrying capability using the linear method and result inclines to unsafety, and the nonlinear finite element method which was used to caculate the aerostatic stability is more exact than the linear method, and the nonlinear finite element method has the advantage of tracking the whole process of structure buckling.