Experimental validation of the design formulas for vibration control of stay cables using external dampers

Transversely installing the dampers on the stay cable has been widely adopted to control its excessive vibration. However, the optimum damper size and its damping efficiency is subject to the effect of damper parameters, including the damper coefficient, damper inner stiffness and support stiffness, damper concentrated mass. Based on the attainable damping-ratio formulas of the stay cable–damper system proposed by authors, this study carries out a serials of experimental study on the cable-damper system to investigate the effect of the above-mentioned damper parameters and to consolidate the accuracy of the proposed damping-ratio equation. A scaled sagged stay cable has been built, and a small-size shear-mode viscoelastic damper has been developed. Results indicate that the larger damper stiffness and the lower support stiffness degrade the achievable damping ratio. Increasing the damper mass properly seems to improve the achievable damping ratio but still needs more full-scale test verification. The sag effect of the cable reduces considerably the attainable damping ratio for the first-order mode while affect marginally for the higher mode. Experimental results of the attainable damping-ratio considering the effect of the damper parameters commonly align with the theoretical values from the design formula. Therefore, the design formula is qualified to facilitate the design of the damper size.