Design of viscous dampers targeting multiple cable modes

Rain–wind induced stay cable vibrations may occur at different cable eigenfrequencies. Therefore, external transverse dampers have to be designed for several target cable modes. The resulting modal damping ratios have to fulfil Irwin’s criterion for minimum Scruton number such that rain–wind induced vibrations can be excluded. For this situation, this paper presents a systematic and easy applicable design procedure for linear viscous dampers that respects Irwin’s criterion, minimizes the damper position and leads to almost minimum variance of the target modal damping ratios. Minimum damper position is preferable from the aesthetic point of view, and it minimizes the installation costs, reduces the damper support flexibility and thereby increases the damper efficiency. Minimum variance of the target modal damping ratios maximizes the safety against large amplitude vibrations due to the unpredictability of the predominant mode.