Impact of Cable-deck Interaction on the Efficiency of External Damper in Controlling Stay Cable Vibration on Cable-Stayed Bridges

External dampers are widely used to control vibrations of stay cables on cable-stayed bridges. In general, the estimation of the damping of a stay cable in a cable-damper system is done based on the assumption that the bridge stay cable has fixed supports at both ends and the damper has a fixed support on the deck. But long-span bridges experience frequent bridge-girder vibrations under dynamic loadings due to long span length, light weight and flexible nature. Therefore, the assumptions of fixed support for the cable and damper is no longer valid in the case of long-span bridges.;An analytical model has been proposed in the current study to determine the damping property of a bridge stay cable when attached with a damper, by considering the effect of bridge-deck vibration on the cable and the damper. The static and the dynamic behaviour of the cable-damper-deck system have been simulated in the model. The validity of the model was verified by assuming a very rigid equivalent beam and was compared with the results obtained from a cable fixed end case. A Matlab program was developed to perform matrix calculations and iterations associated with the model. Associated dynamic analysis was carried out using the finite element model in ABAQUS 6.9.;Case studies were conducted to investigate the effect of cable-deck interaction on the damper efficiency for cable-stayed bridges with different span lengths. The range of main span length that requires the consideration of bridge-deck vibration for the estimation of damper efficiency was proposed.