MECHANICAL DAMPING SYSTEMS FOR TRAFFIC SIGNAL MAST ARMS

Several mast arm failures have been observed in Florida and other states from fatigue caused by wind-induced vibrations. An economical method to mitigate the effects of wind induced vibration on these types of structures is to install mechanical damping systems directly on the mast arm. These devices limit the amplitude and duration of vibrations resulting in an increase in the design life of the structure. This report describes the development and testing of several different damping devices for cantilevered mast arm structures. Prototype damping devices were tested on an 11.3 m (37 ft) mast arm constructed in the Structures Laboratory at the University of Florida. Successful devices were then field tested on several different lengths of mast arms (11.0 m to 21.4 m) to determine the effectiveness over the full range of installations. The optimum device developed was relatively insensitive to the natural frequency of the mast arm and consists of a tapered steel tube, weight and spring system.