Wind-induced vibration of a traffic-signal-support structure with cantilevered tapered circular mast arm

Traffic-signal-support structures with cantilevered mast arms are known to exhibit large-amplitude vibrations under certain wind conditions. Previous investigations of the problematic vibrations have primarily focused on the aerodynamics of the signal heads of various configurations. Based on full-scale measurement of a traffic-signal-support structure, the role of the cantilevered mast arm in the aeroelastic vibrations is studied. Contrary to previous reports that the vibrations are due to galloping of the traffic signals, this study reveals that the aeroelastic interaction between the wind and the mast arm is critical in the excitation mechanism of the vibrations. Two types of excitation mechanisms, vortex-shedding at low wind speeds and buffeting at high wind speeds, were identified.