Monitoring-based analysis of wind-induced vibrations of ultra-long stay cables during an exceptional wind event

Ultra-long stay cables characterized as high flexibility are prone to large-amplitude vibrations. Much attention has been paid to the vibrations of stay cables under normal wind conditions in the past decades, while the dynamic response under extreme winds is reported rarely. This study investigates the exceptional wind-induced vibration of the stay cables of a kilometer-level cable-stayed bridge based on the monitoring data. The mean wind velocity and extreme wind duration are firstly obtained using the wind records of the structural health monitoring system (SHMS). The effects of the turbulence intensity and mean wind velocity on the cable vibrations are then analyzed. To explore the motion trajectory features, the in-plane and out-of-plane dynamic displacements are estimated by an acceleration-based approach. Besides, the modal properties, including the frequencies and damping ratios, are identified. The result shows that the stay cables present multi-modal vibrations with frequencies higher than 3 Hz, which is different from rain-wind-induced vibration (RWIV). The out-of-plane vibration amplitude under the extreme wind is much larger than that of the in-plane due to the absence of dampers. Furthermore, the out-of-plane damper is suggested to mitigate the large-amplitude vibration of ultra-long stay cables under exceptional winds.