Research Of Parameters Influencing The Flutter Derivatives Of Truss Bridges

Flutter is the most serious destruction of the bridge caused by wind-induced vibration. Once the vibration happened, it will result in the complete destruction of the whole structure. Flutter derivatives are the core analysis in Scanlan thorey of flutter, and will determine the unique characteristics-flutter critical wind speed directly. The main contents are as follows:First, this thesis gives the classical theory of coupled flutter, flutter separated flow theory and theory of three-dimensional flutter a introduction in detail. Secondly, the time domain identification method in the flutter derivatives have simply introduced, including ITD method, MITD method, ULS method, MLS method, ILS method and SEO-ILS method. As the experimental conditions, the MLS identification method is selected.Taking the Liujiaxia bridge section model as an object, this dissertation studies the impaction of damping ratio, turbulence intensity and aerodynamic measure respectively on the flutter derivatives through series of tests. According to the comparison of classification, conclusions are obtained as followed:(1) In the comparison of damping ratio tests, the flutter derivative curves law at 0°and±3°angles of attack are inconsistent. With the increase of torsional damping ratio, the combined effect of flutter derivatives at the 0°and -3°angles of attack is quite obvious, while the effect at +3°angle of attack is relatively little.(2) By setting up different grids in the upper of truss section model to generate 0.08,0.10, 0.13 three kinds of turbulence intensity of the turbulence field in the wind tunnel, and comparing the flutter derivative curves under turbulent flow and uniform flow obtained the following results:there is no significant change in the trend of flutter derivative curves, but the values vary greatly.(3) Setting central stabilizer, inner baffle and flange plate in the truss section model, author obtained the following results by contrast the flutter derivative curves:the impact of aerodynamic measure on flutter derivatives is very obvious. With the different angle of attack, the effect is different.