Evaluation of viscous dampers for stay-cable vibration mitigation

Many cable-stayed bridges around the world have displayed excessive and unanticipated vibrations of the main stays, often associated with the simultaneous occurrence of wind and rain, and mitigation of these vibrations has become a significant concern in cable-stayed bridge design and retrofit. Much of the previous research on this problem has been conducted using wind tunnels, and there have been relatively few opportunities to measure the vibrations at full-scale. This paper presents results from long-term field measurements of cable vibrations on a cable-stayed bridge in the United States. Characteristics of different types of measured vibrations are summarized, and the effectiveness of passive linear dampers in vibration suppression is evaluated by comparing response statistics from two stays before and after installation of dampers and by investigating in detail the damper performance in a few selected records corresponding to different types of excitation. The dampers are observed to be quite effective, but a fundamental limitation of mode-dependence in linear damper performance is emphasized, and some potential advantages offered by a nonlinear damper are discussed.