Spacers combined with dampers for the wake-induced vibration mitigation of two parallel hanger cables

Cable wake-induced vibrations (CWIV) and tower column wake-induced vibrations (TWIV) are two types of detrimental vibrations for long hanger cables in suspension bridges. In this study, the hybrid control strategy that combines spacers with dampers is proposed as a potentially effective method for mitigating these vibrations. To validate this hypothesis, the control performance of spacers combined with dampers for both CWIV and TWIV is evaluated through aero-elastic wind tunnel tests. The universal characteristic equation of the hanger cablespacers-damper system is derived. On this basis, modal behaviors of hanger cables with spacers and dampers are investigated to demonstrate the control principle of the hybrid strategy. The three-dimensional aero-elastic models of hanger cables, spacers, and the eddy current damper are designed and manufactured to evaluate the combined control performance of spacers and dampers for CWIV and TWIV by a series of wind tunnel tests. In addition, the effect of modal damping ratios on the control performance of TWIV is investigated by an oil damper installed at a high location on hanger cables. The results showed that spacers combined with dampers are more effective than spacers alone in mitigating CWIV and TWIV. The hybrid control strategy can suppress the vibration response of CWIV to an acceptable level, but a larger modal damping ratio in the first global mode (approximately 3%) is required to mitigate TWIV.