Stagnation point-induced vibration on ultra-long stay cables and the vibration control by using a novel stockbridge damper

Abstract

A peculiar wind-induced vibration with large acceleration amplitude, super-high and narrow frequency bands was observed on ultra-long stay cables after one-year-more field monitoring on the Sutong Bridge. The vibration was found extremely detrimental and cannot be suppressed by a single damper system. Based on this, it is first demonstrated that the vibration is a unique vortex-induced vibration resulting from the damper installation position, and which is named stagnation point-induced vibration (SPIV). Subsequently, a Stockbridge damper (SBD) scheme, usually used on transmission lines, is introduced to suppress the SPIV: the dynamic model of the stay cable-SBD system is established; the additional damping ratios are calculated based on the proposed model and the equations; moreover, parameter optimisation analyses of the SBD are conducted. Then, a real SBD is designed, produced, and finally installed on an actual stay cable with a length of 551 m based on the optimum parameters. Finally, with six months of field vibration monitoring data, the proposed dynamic model and the SBD damping scheme are demonstrated effective to the suppression of the detected SPIV. The study is expected to give a practical vibration control reference for ultra-long stay cables that are more than 500 m.