RESEARCH ON COUPLING OF THE VORTEX-EXCITED RESONANCE AND GALLOPING OF THE BLUFF BODY WITH LARGE SLENDERNESS RATIO

Vortex-induced resonance and galloping are two common types of wind-induced vibrations for the slender structures. When the critical wind speed of galloping falls in the lock-in range of vortex-induced resonance or just closely, these two different vibrations are prone to be coupled. The coupling of these two types of vibrations is theoretically analyzed, and prediction models are formulated accordingly. Based on the investigation of three engineering examples of slender structures, the critical wind speed of galloping and lock-in range of vortex-induced resonance are respectively evaluated with the aerodynamic parameters identified from both numerical simulation and wind tunnel test. The actual vibration curves obtained from wind tunnel test are quite consistent with those from the prediction models, which demonstrated the possibility of the coupling of vortex-induced oscillation and galloping under certain conditions. Moreover, it is found that the negative aerodynamic damping originated from the two different mechanisms is cooperated and can partly cancel the mechanical damping of a structure. As a consequence, the amplitude of vortex-induced resonance will be amplified, and the critical wind speed of galloping is reduced.