A Study on Countermeasures against Wind-Induced Cable Vibrations in Cable-Stayed Bridge by Changing Vibration Modes

Vibrations of stay cables are often induced by wind because of their aerodynamic instability. They must be suppressed to prevent cable fatigue and to allay passenger fear. Although various countermeasures have been developed, totally effective one has not yet been established. In this paper, the authors propose a new method using a permanent magnet. A magnet installed near the end of the cable changes the vibration modes passively by repeating motions of constraining and releasing cables. With this method, growth of the unstable fundamental vibration mode is prevented by dissipating energy of higher stable modes. Comparing with other methods, it is expected to improve low temperature characteristics, maintenance and manufacturing cost. After describing the principle, fundamental studies on energy transferring mechanism were carried out and it was verified that the lower modes energy is distributed to the higher modes when the cable is released from the magnet. The effectiveness of this method was confirmed by wind tunnel tests and numerical simulations.