Influences of Attack Angles on Aerodynamic Derivatives and Flutter Characteristics of Flat Box Girders

Abstract

The flutter response of Nanjing Fourth Bridge flat box girder under different wind attack angles was tested in detail through sectional model test. The evolution of unsteady and steady critical amplitude with wind speed was discussed. Based on the amplitude envelope of the flutter response and the Hilbert transform, the amplitude- dependent modal damping of the system is identified, and the mechanism of the flutter mode change in the wind angle of attack is initially explained. Secondly, the modal parameters of the system under different wind attack angles were extracted. Based on the bimodal coupled flutter analysis method, the nonlinear flutter derivatives of the section under different wind attack angles were identified, and the change law of the amplitude dependence of the key flutter derivatives on the wind attack angle and the potential influence on the flutter morphology and characteristics of the section were studied. Finally, the effect of wind attack angle on uncoupled and coupled aerodynamic damping is analyzed by deconstructing the modal damping one by one, and the dynamic mechanism of the differential flutter performance caused by fractional damping is illustrated.