VIV Properties of <i>π</i> -Shaped Bridge Sectional Model: Dependence on Torsional-Bending Frequency Ratio
Zhixiong Wang, Zhitian Zhang
Abstract
The vortex-induced vibration (VIV) properties of a π-shaped bridge girder are addressed in this study through wind tunnel tests. Attention is paid to the influence of torsional-bending frequency ratio on the VIV, while the mass-damping property (Scruton number) of the vertical motion remains unchanged. The torsional-bending frequency ratios of the model covered in this study were 0.872, 0.971, 0.988, 1.035, 1.085, and 1.245. The results show that, when the ratio is close to 1.0, the girder exhibits coupled vibration in the vertical and torsional directions. However, the coupling significantly reduces the vortex-induced vertical amplitude, which had been supposed to remain unchanged, owing to a fixed Scruton number. Further, the results indicate that the torsional motion results not only in the transference of a small amount of energy from vertical to torsional vibration, but also in a substantial reduction of the total amount of mechanical energy trapped by the system from the wind field. The energy reduction effects should be understood as a result of the altered flow pattern around the section, which is caused by coupling of the model's degrees of freedom.