Traffic, sign, and lighting structures are typically characterized by their high flexibility and extremely low damping which make them particularly susceptible to wind-induced vibration. Various types of wind loading, including galloping, vortex shedding, natural wind gusts, and truck-induced gusts, can result in vibration of these structures. Furthermore, low natural frequencies of these structures can result in the vibration phenomenon called resonance. The large amplitude and cyclical response from the various wind-induced vibration, results in repeated live load stress variations which can significantly reduce the fatigue life of these structures.
Valmont Industries has developed new technology using vibration theory to effectively reduce the daily vibration stress range from wind excitation thus increasing the fatigue life of the structure. The Valmont damper reduces vertical arm displacement normally above 90% caused by wind, wind induced vibration (galloping and vortex shedding), and truck gusts, as designed per AASHTO “Standard Specifications for Structural Supports for Highway Signs, Luminaries, and Traffic Signals” Section 11 Fatigue Design. Use of this device will improve safety to the traveling public, extend the life of new and existing structures, and lower maintenance, inspection and repair costs resulting in more efficient traffic, sign, and lighting structures. The city of Omaha has already incorporated this device into their design standards.
The presentation will cover the development, lab testing, and field testing of the vibration damper.