A stay cable with viscous damper and tuned mass damper

Stay cables in cable-stayed bridges are vulnerable to dynamic excitation because their intrinsic damping is very low. The cables have often been exhibiting undesirable and excessive vibrations which result in increasing maintenance frequency and disruption to normal operations of the entire bridges. Mitigation of undesired cable vibration can be achieved by attached damping devices, such as viscous damper, near the anchorage. Although viscous damper has shown effectiveness in reducing cable vibrations, it is not the most effective method due to geometric constraints. Tuned Mass Dampers (TMD) were proposed to overcome the deficiency of viscous damper because they can be placed anywhere along a cable. However, the drawback of TMD is its limitation in being only effective for a single-tuned vibration mode. This paper presents a hybrid damper system, combining a viscous damper and a TMD, to overcome the shortcoming of single type of dampers in order to improve effectiveness and robustness in suppressing cable vibration of cable-stayed bridges. Oscillation parameters of cable-damper system were investigated using an analytical formulation of the complex eigenvalue problem. An example is provided to demonstrate the effectiveness of the combination of a viscous damper and a TMD for cable vibration reduction.