Observations of bridge stay cable vibrations in dry and wet conditions: A case study

Abstract

The characteristics of wind- and rain-wind-induced vibrations of bridge stay cables are studied by using ambient vibrations records acquired on a cable-stayed bridge. Mean wind speed and wind-cable angle, as well as the occurrence of rainfalls, were investigated to diagnose a possible excitation mechanism promoting the onset of large heave amplitude oscillations, which were occasionally reported. Light rainfall, mean wind speed values between 8 ms and 12 ms and wind-cable angle ranging to were found to be critical conditions for the onset of large amplitude vibrations for the cases at hand. A single-mode response (eigenmode 3) associated with reduced velocities around 35 was generally activated during large cable oscillations (peak-to-peak amplitudes of twice the cable diameter) in wet conditions. The simultaneous video camera recordings also contributed to an improved understanding of the upper rainwater rivulet formation and the mechanism of stay cable vibrations in wet state.