Rain Wind Induced Vibrations of Stay Cables in a Single Tower Bridge

This paper investigates Rain-Wind Induced Vibrations (RWIV) of the stay cables of the Stavanger City Bridge, where the stays are arranged in bundles connected by rigid cross-ties and occasional large-amplitude displacements may affect long-term structural integrity and user comfort. Previous short-term campaigns established baseline weather conditions for RWIV, but discontinuation of direct cable monitoring required an alternative method for long-term assessment. Using a six-year dataset of synchronised on-site weather measurements and bridge deck accelerations, together with 81 days of direct cable response data, this study develops a reliable indirect detection approach. Power Spectral Density (PSD) and cross-sensor complex coherence analyses of the global deck response are used to identify RWIV signatures linked to target cable eigenmodes. The refined criteria identify two distinct susceptibility clusters associated with two considered cables in the domain described by wind speed and cable-wind angle. Each cluster is parametrised by a thresholded bivariate normal model, with decision boundaries defined by 10th-percentile density cut-offs. Comparison with wind-tunnel studies shows reasonable agreement for the longer cable, whereas the shorter cable's cluster lies outside the previously documented envelope. A longitudinal assessment indicates a marked reduction in RWIV occurrence after 2021. Although weather-based criteria also show a slight reduction in favourable conditions, the decrease in structurally identified RWIV is substantially larger, indicating reduced structural susceptibility, plausibly linked to changes in cross-tie configuration.