Characteristics and Suppression Neasures for Soft Flutter of Main Girder with П-Shaped Cross Section

Main girder with П-shaped cross section has aerodynamic blunt body structure, and under the nonlinear self-excited force, it is vulnerable to soft flutter. To study the effects of various aerodynamic measures on soft flutter performance of this main girder, the aerodynamic performance of a cable-stayed bridge was used through wind tunnel test of sectional model. The results show that soft flutter of the main girder is a coupled two-degree-of-freedom torsional-bending vibration with single frequency. With the increase of wind speed, the degree of vertical vibration decreases first and then increases. Setting wind fairings can increase the value of R. The amplitude of soft flutter follows a normal distribution, and the amplitude range varies with wind speed and angle of attack. Soft flutter is most likely to occur when the angle of attack is negative. Setting auxiliary facilities on the bridge deck can enlarge the critical velocity, and reduce the soft flutter amplitude and the amplitude growth rate. Setting wind fairings can reduce the vibration response of soft flutter, and the soft flutter performance can be improved by sharpening wind fairings. With the wind fairing angle sharpening, the critical velocity of soft flutter tend to rise but the amplitude of soft flutter tend to fall. Setting the central stabilizer at the base of the bridge deck has am unobvious effect on the soft flutter performance of the main girder.