Wind Tunnel Experimental Investigation And Numerical Simulation On The Flutter Characteristic Of A Long-span Suspension Bridge

Nowdays, with the suspension bridge developing into an extra long-span and flexible phase, the problem of wind-induced vibration has become increasingly prominent. The research is supported by the National Natural Science Foundation Project. This paper based on the engineering background of long span suspension bridge ——Cuntan Yangtze River Bridge in the western mountainous area, studied its flutter characteristics, including identifying flutter derivatives and critical flutter velocity. The study adopted two methods: measuring wind tunnel test and numerical simulation calculation, and the results of two methods of research were analyzed. The main girder aspect ratio of Cuntan Yangtze River Bridge is 12, this kind of wide flat steel box girder is rare. Some rules of flutter characteristics are summarized through the research. To provide reference for similar engineering and related research work in the future. The specific research works include the following aspects:(1) To describe the basic theory of flutter derivatives, and analyze the theoretical solutions of flutter derivatives of ideal flat. Then introduced the identification method of flutter derivatives, include two identification methods: free vibration and forced vibration. And expounded the process of numerical simulation calculation of flutter derivatives and the calculation method of critical flutter velocity.To introduce the basic theory of Computational Fluid Dynamics(CFD), outline the forms of mesh and boundary conditions. Selected the turbulence model and the calculation of incompressible flow field. And introduced the software of the FLUENT.(2) Firstly, using the FLUENT to simulate study the flutter derivatives of ideal flat, compiled UDF program and used dynamic grid principle, accessed to the vertical and torsional drive data of aerodynamic. Then using the MATLAB procedures to identify eight flutter derivatives according to the principles of least squares method, and compared to the theoretical solution of Theodorsen. To verify the feasibility of numerical calculation.(3) To design the parameters of the main girder section model and produce the wind tunnel test model, then studied the experimental performance of flutter in the wind tunnel. Firstly, measured the critical flutter velocity. Secondly, proceeded the test of flutter derivatives identification in free vibration, and collected the displacement-time data of vertical and torsional. Finally, used the MATLAB procedures to identify eight flutter derivatives according to the principles of least squares method.(4) Using the FLUENT to study the flutter derivatives of the main girder section model, obtained numerical results of eight flutter derivatives, and obtained its critical flutter velocity magnitude according to the Seanlan calculation method. Then based on the main frame section, researched by changing the aerodynamic shape to influence the aerodynamic shape of the main beam section flutter performance. Finally, compared the results of numerical simulation and wind tunnel test.(5) Using the finite element software ANSYS to establish a full-bridge three-dimensional model, calculated the dynamic characteristics of completed state and typical construction state. analyzed the flutter stability of completed state and typical construction state according to the results of the dynamic characteristics. To provide a reliable basis of the assessments for flutter stability of bridge.At the end of the paper, the research conclusion of flutter characteristics is summarized. And flutter stability of the Cuntan Yangtze River Bridge is verified to meet the demand. It provides some reference value for the practical engineering application.