Numerical Calculation Method For Flutter Critical Wind Speed And Flutter Derivates Of Long-span Bridge Streamlined Steel Box Girder

With the development of long-span bridges,the bridge structure becomes more and more flexible,and the wind-induced vibration of bridges becomes more and more prominent.Among all kinds of wind-induced vibrations,flutter is a divergent self-excited vibration,which can cause great loss of life and property.In this thesis,under the framework of Scanlan flutter theory,the numerical calculation method of flutter of long-span bridges was studied around the critical wind speed and flutter derivatives.The main work is as follows:1.The development history of long-span cable-stayed bridges and suspension bridges was introduced,and the wind resistance of bridges was summarized.The theory of bridge flutter analysis was expounded and the research status of flutter critical wind speed and flutter derivative at home and abroad was described in detail.2.The semi-inverse method for solving the critical flutter wind speed was introduced and transformed into an optimization problem.In order to solve the optimization problem,two hybrid particle swarm optimization algorithms which can consider both global convergence and local convergence was proposed and applied to the solution of the critical wind speed of flat plate structure.3.Based on the computational fluid dynamics method,the flutter derivatives of the flat plate were identified by State-by-state forced vibration method.Firstly,the flutter derivatives of flate plate under the multi-frequency input signal were identified.Then based on the ARMA model,the flutter derivatives under the exponential signal,3211 signal and Chrip signal were identified.Finally,all the results were compared with the theoretical solution.4.The hybrid particle swarm optimization algorithm and the identification method of flutter derivatives under multi-frequency signal were applied to the flutter analysis of a longspan suspension bridge streamlined steel box girder.According to the calculation results,the influence of the guardrail and the inspection vehicle track on the flutter performance of the steel box girder was analyzed.5.The ARMA model was used to describe the whole fluid-solid system,and the relationship between structural state and aerodynamics was obtained.The fourth-order RungeKutta method was used to solve the vibration equation of the structure,and the numerical calculation of fluid-solid coupling was realized.The flutter of the streamlined steel box girder is simulated by this method.