Analysis of Interaction between Vibration Modes
of Single Cable Due to Aerodynamic Damping
Hee Dong Goh
The importance of the aerodynamic damping of cable members is growing, as the recent bridges are being designed with long span. However the formula for the aerodynamic damping ratio shown in the current design guide is rather simple based on the single degree of freedom assumption. Because the aerodynamic damping is function of the relative velocity between the wind and cable motion, this study performed and discussed about more accurate calculation of aerodynamic damping ratio, respect to two dimensional motion and the sudden drop of the drag coefficient in the critical Reynolds number region.
Vibrational modes of the taut cable change along the angle of the wind due to the interactions between the modes. 45% error may occur for the worst case. In addition, a negative damping ratio can be expected when the cable is under the critical Reynolds number region.
The criteria for the geometrical and meterial condition of the cable and the velocity and angle of the wind is presented in this study, based on the normalized Irvine Parameter.
Cable, Aerodynamic damping, Drag force, Vibration mode, Quasi-steady theory