Abstract
The effect of aerodynamic damping on the damping ratio of a four-bundled conductor was examined by comparing the observed damping ratio and theoretical formula of aerodynamic damping. The observed damping ratios of various vibration modes were obtained using the random decrement technique from a tension data conductor observed at various wind speeds. The theoretical formulas of aerodynamic damping in the horizontal, vertical, and torsional directions were derived from a single-degree-of-freedom motion equation and the definition of the quasi-steady aerodynamic force of each direction. The observed damping ratio increased proportionally to the wind speed, as is the case with the theoretical formula. However, the observed damping ratio tended to exceed the theoretical formula. The theoretical formula, in which the constant margin is added, shows good agreement with the observed damping value. The result suggests that total damping comprises constant structural damping and aerodynamic damping, which is proportional to wind speed. It is possible that the structural damping can be identified from the approximation formula of the observed damping ratio.
