A review of impact dampers to control cross wind vibration of structures due to vortex shedding

This paper reviews the application of chain, ball and beam impact dampers to control cross wind induced vibration of structures. These structures can vibrate with large amplitudes in the cross wind direction when the Scruton number has an insufficient value to prevent high amplitude vibrations and when the Strouhal number achieves a critical value. Thus, added damping is required to reduce the amplitude of motion to prevent possible fatigue failure of the structure in question. Impact dampers are relatively inexpensive and, in general, do not require exact tuning as for the case of tuned mass dampers. These two factors make impact dampers attractive as add on damping for slender structures. Important variables considered in the design of the impact dampers will be discussed and emphasis will be made on the need for testing of the largest possible experimental model of the structure, if possible, due to some of the unknowns, as for example, the coefficient of restitution of the impacting bodies required to provide damping.