Application of TMD systems in vibration control of stay cables subjected to seismic loading

Stay cables are crucial elements that greatly influence the structural behavior of cable stayed bridges. Cable elements are susceptible to external excitations due to their high flexibility and low inherent damping. Though traditional mechanical dampers, with one end connected to the cable and the other end to the deck, are useful for vibration reduction, their installation position restrictions make their efficiency low. Tuned mass dampers (TMDs) which can be placed anywhere along cables, are more effective for cable vibration mitigation. In this study a two dimensional stay cable with sag coupled with the TMD is simulated in OpenSees software. Nine control systems with differences in number of TMDs, mass ratio, and TMD location are utilized. The control systems are subjected to different external seismic excitations and their efficiency is evaluated by comparing the system's responses with those of the uncontrolled system based on three different criteria. The results show that the implementation of the control systems can effectively reduce the seismic response of stay cables by reducing the maximum displacement of the cable by up to 76 percent. The optimum frequency of TMD systems is close to the fundamental natural frequency of cable. Increasing the mass ratio of TMD leads to an increase in effectiveness of control system, but the economic and practical limitations usually prevent us from using mass ratios more than 5 percent. The optimal location for installing the TMD is at the midpoint of the cable in which the maximum displacement is more likely to happen. Utilizing additional masses in quarter points does not bring out a remarkable promotion in the efficiency of control system

Keywords:

Stay cables , Vibration control , Tuned mass damper , seismic behavior