Mechanism And Parametric Study On Nonliear Aerostatic Instability Of Long-Span Suspention Bridge

With the advancement of technologies and materials, suspension bridges are developing towards the target of longer span and slimmer structure, thus posing a threat to the dynamic and static response resulted from the wind load. According to the wind tunnel test at home and abroad, the phenomenon that static response appears in advance of dynamic response has been observed. Static instability is the key problem in the wind resistance design of long span suspension bridges, and therefore it is meaningful to study the static action and instability law of long span suspension bridges under strong wind.The geometric nonlinearity and wind load nonlinearity are considered in the thesis. An ANSYS program based on the iteration of time and wind load is written to analyze the aerostatic stability of long-span suspension bridges, and the reliability and stability of the program have been proved in the wind tunnel test of a long-span suspension bridge.In the thesis, the nonlinear whole-process analysis of the aerostatic stability of Humen No.2 Bridge is carried out with the ANSYS program, which could reveal the law of the structural deformation variation under different wind velocities. Besides, by altering the initial wind attack angle and adjusting the three component coefficient (number or curve slope), parametric influence of nonlinear aerostatic stability for the bridge has been studied. Finally, the influence of nonlinear factors on aerostatic stability is discussed.According to the results, it is more accurate to take the geometric nonlinearity and the wind load nonlinearity into consideration while calculating the critical aerostatic instability velocities and the bridge deformation curve with the increment of wind speed. In the case of aerostatic instability, while the attack angle increases, the critical wind velocity decreases and the deformation of the bridge as well as the gradient of the deformation curve would increase. The three component coefficient are important factors to the aerostatic stability of the bridge.