The oscillation of the cables of cable supported bridges such as cable-stayed bridges shortens the life span of bridges due to damage effect on the strand and cover of the cables. Cable vibration results from various factors, but the main factor is th...
The oscillation of the cables of cable supported bridges such as cable-stayed bridges shortens the life span of bridges due to damage effect on the strand and cover of the cables. Cable vibration results from various factors, but the main factor is the excitation of cable anchorage due to the vibration of superstructure and main tower which results in parametric resonance and external resonance. In particular, it is impossible to control parametric resonance by the damping force of cable itself because parametric resonance amplitude is very large. This study deals with methods to mitigate the vibration due to excitation by the oscillation of superstructure and main tower. For this study, each nonlinear effect of cable model which is subject to support excitation is identified and vibration model of cable where a damper is established is considered for the most dominant nonlinear effect in actual bridges. Cable model where a damper is established is made allowance far cable sag, elastic strain and inclination in addition to nonlinear vibration effect such as parametric vibration. In order to analyze the effectiveness of damper, the response of cable system is studied by varying the cable sag, excitation amplitude, damper capacity and damper location. Cable which is subject to support excitation has parametric and external vibration by transverse oscillation of superstructure and main tower. So that the damping force of cable itself can not decrease response amplitude for a particular excitation frequency. On the other hand, the proper damper which connects near the cable anchorage to superstructure can increase cable damping ratio for first vibration mode up to maximum 1%. This damper can lessen efficiently cable vibration subject to external excitation. However, it is impossible to mitigate the vibration by single damper when cable is subject to resonance. Also, frequency avoidance phenomena which happens to cable with particular sag ratio decrease achievable damping ratio of a damper by 65% of optimal damping ratio. When considering the installation and effectiveness of damper, it is most optimal to locate the damper at 0.02L~0.03L from anchorage.