Wake-induced vibrations of tandem main cables: Insights from flexible and rigid models in wind tunnel tests

In order to accommodate the increasing span lengths of suspension bridges, the scheme of adopting tandem main cables was proposed. To provide valuable insights into the wake-induced vibration (WIV) characteristics of tandem main cables with variable center-to-center spacings from the pylon saddle to the anchor, wind tunnel tests were conducted using two sets of flexible models with different scaling ratios and one set of rigid segmental models. The effects of center-to-center spacings between upstream and downstream cables, wind angle of attack, and turbulence intensity on WIV of the model cables are examined. The effectiveness of rigid connectors on suppressing the WIV of the model cables was also evaluated. The findings indicate that the tandem cables with variable center-to-center spacings are susceptible to severe WIV in both smooth flow and turbulence flow. The vibration amplitudes and dominant modes change with the wind speed and wind attack angle. The occurrence of WIV in tandem cables with variable center-to-center spacings depends on the small spacings between the upstream and downstream cables, while large spacings affect the critical wind speed for WIV. Contrary to expectations, rigid connectors were found to amplify the WIV response in specific condition, emphasizing the importance of evaluating such mitigation strategies in bridge design stage.