Research On Identification Of Aerodynamic Derivatives For Bridge Decks By Wavelet Transform Method

Identification of aerodynamic derivatives for bridge sections is one of the important and difficult issues in the flutter response of long-span bridges. Aerodynamic derivatives are one of the important aerodynamic parameters to describe aerodynamic performances of long-span bridges. Refined analysis of wind resistance of bridges requires a more advanced system identification. Based on theoretical analysis, numerical simulations and wind tunnel tests, the in-depth study on aerodynamic derivatives recognition of bridges and influence parameters of aerodynamic derivatives are conducted. In sum, the main contents are concluded as follows.(1) The thesis reviews and summarizes wind-induced vibrations of long-span bridges, flutter analysis of bridges and aerodynamic derivative identification method. The problems of identification of aerodynamic derivatives are pointed out and the contents of the thesis are cleared.(2) The basic theory of wavelet transform is discussed in detail. Highlights the complex Morlet wavelet function and for non-orthogonal wavelet transform fast algorithm, which laid a theoretical foundation for the next study of aerodynamic derivatives and its identification method.(3) Modal parameters identification using wavelet transform with high precision accuracy, strong anti-noise characteristics and easy program realization. Using wavelet transform multimode complex mode identification method, complex Morlet Continuous Wavelet Transform (CMor-CWT) Identification is proposed to identify aerodynamic derivatives of bridge decks and theoretical basis and implementation steps are given.(4) The complex Morlet continuous wavelet transform (CMor-CWT) uses Matlab programming.Through numerical simulation examples and the bridge section model tests, compared with other aerodynamic derivatives identification methods. Verify the accuracy and reliability of the method, and the identification process has the advantages of visualization.(5) Based on CMor-CWT identification method, take a series of aerodynamic measures and change damping ways to improve the flutter stability of the original bridge truss sections. Analysis of the impact of aerodynamic measures and damping on aerodynamic derivatives(6) Based on the passive grid technology, this thesis builds several different turbulence properties of turbulent flow field. The aerodynamic derivatives in turbulent flow field are compared with uniform flow. Analysis of turbulence effects on aerodynamic derivatives. It is proved that the method to identify the aerodynamic derivatives in turbulent flow field is applicability and reliability.