High-mode vortex-induced vibration of stay cables: monitoring, cause investigation, and mitigation

Herein is described a case study using long-term field monitoring data from a cable-stayed bridge to investigate the cause of high-mode vortex-induced vibration (VIV) observed in stay cables. Wind characteristics and dynamic responses of girders and stay cables were analyzed to investigate two possible vibration sources–interactions with girders and vortex shedding. To this end, a modal decomposition procedure that included automated peak picking and successive band-pass filtration was proposed. These novel steps revealed a relationship between the shedding frequencies of stay cables and corresponding critical wind velocities. The main cause of large-amplitude VIVs was diagnosed using a novel damping identification procedure that consisted of automated modal decomposition, temporal correlation, and optimization-based curve fitting techniques. The damping identification results demonstrated how the modal VIV amplitudes of stay cables have a strong dependency on damping capacity. The effectiveness of Stockbridge dampers in mitigating high-mode cable VIVs was subsequently examined through field application and comparison analysis during a typhoon. The unique interaction between stay cable vibrations and the buffeting response of bridge girders observed during this period was additionally discussed.