Research On Flutter And Static Wind Of Great-span Bridges

The modern bridge structure becomes longer,more flexible,more delicate,and thus will be more sensitive to wind action. The main effects of wind-induced include flutter,buffeting,galloping and vortex-induced vibration in long span bridges。The flutter becomes more important for making a destructive damage to the bridge structure in a short period time. Based on the existing method of flutter analysis, the flutter of long span bridge has been studied through three aspects in the article. In addtion ,the aerostatic stability of long span bridges cannot be ignored ,and the calculation of nonlinear static wind-resistance of long span bridges is studied in the article.The main research contents are as follows:(1)Investigation of optimal solution of the flutter equation. According to Scanlan flutter theory,the two-dimensional flutter equation of bridge in air is established and a reduction solution method is proposed. by reasonable assumptions and simplify analysis,a reduction solution is proposed through making both sides of the real and imaginary parts equal.(2)ANSYS and MATLAB programs are developed for flutter analysis. The flutter frequency analysis is programmed in ANSYS / APDL and MATLAB language,and a classical flat example is taken to prove the two programs'correctness and validity。The contribution of the main modal is discussed through some engineering examples and the influence of the flutter critical wind speed during into a bridge period is also studied when the structure damping is different。(3)The establishment of simplified critical flutter wind velocity formula. According to the long-span bridge's vertical fundamental frequency formula and standard based frequency formula by "Road and Bridge Wind Design Standard" ,the simplified critical flutter wind velocity formula for calculating is established through Van der put formula and some engineering projects.(4) Investigation of nonlinear static wind-resistance. The method of internal and external incremental iteration is used and the nonlinear static wind-resistance program of great span bridges is developed by using ANSYS/APDL language when considering the nonlinear effects of structure and static wind load. Under different working conditions, the effects of bridges'parameters on long-span bridges'nonlinear aerostatic stability are also studied .