Aerostatic Stability Of Asymmetrical Long-span Suspension Bridge

China has a large mountainous area. With the development of the highway to the mountainous area, in the construction of suspension bridge due to a variety of factors limit such as environmental factor, asymmetrical tower suspension bridge has been more widely used. However, the studies are still relatively scarce. In this paper, it is adopted that the relatively mature inner-and-outer incremental iterative method. A asymmetrical long-span suspension bridge is chosen as an engineering example and a nonlinear finite element method through ANSYS APDL language is presented to calculate directly the critical wind velocity for the aerostatic instability of suspension bridges and find the characteristics of the aerostatic instability of an unsymmetrical tower suspension bridge. At the same time, we need to analyze the effect of several parameters to finally provide the basis for wind resistant design of unsymmetrical tower suspension bridge. The main contents of this paper are as follows:1. At first, the development history of the aerostatic stability theory is summarized, the linear and nonlinear method of suspension bridge aerostatic stability are introduced. It is described in detail the realization method of using nonlinear method to solve aerostatic stability in ANSYS.2. This paper establish the spatial finite element model of the bridge Puli by ANSYS software. through modal analysis of the bridge, the natural frequencies and modes of the model are obtained and calculated. Modify rise-span ratio and the height of IP point for two pylons based on the original finite element model, and analysis rise-span ratio or the height of IP point for the influence of vibration characteristics by comparison. It is laid the foundation for the analysis of aerostatic stability of an unsymmetrical tower suspension bridge.3. The whole prosess of the asymmetric and symmetric suspension bridge aerostatic instability are recorded and analyzed by the programming to sum up the instability mechanism of interaction among the main beam deformation, static wind load and stiffness degradation. The characteristics of aerostatic stability of the two structures were compared and analyzed. The analysis show that the both path of aerostatic instability is basically the same.4. The natural wind angle of attrack, static aerodynamic coefficients, geometrical nonlinearity of structure and nonlinearity of static wind load, the wind load of the beam and main cables are analyzed. It makes a research about the influence of them on an unsymmetrical tower suspension bridge and obtains the influence law of different wind angle of attrack and negative wind angle of attrack on the aerostatic stability. It results the degree of influence of static aerodynamic coefficientsand and the wind load of the beam and main cables toward suspension bridge static wind stability. It proves the necessity of considering the impact of geometrical nonlinearity of structure and nonlinearity of static wind load during the analysis.5. Further studies on response pattern of static wind in the condition of changing two parameters rise-span ratio and the height of IP point for two pylons. The analysis shows that the degree of both influence for aerostatic response are relatively small.This paper mainly researchs on aerostatic stability of asymmetrical long-span suspension bridge, and obtains some reasonable and meaningful conclusions. It provides help and reference in wind-resistant design or the relevant research.