Passive Vibration Mitigation for Highway Sign Trusses Susceptible to Wind-Induced Vibrations

Stockbridge-type tuned-mass dampers are commonly used in highway sign and traffic signal support structures throughout the U.S. to reduce wind-induced and truck gust-induced vibrations. Effectiveness of these dampers in mitigating excessive structural vibrations, and thereby preventing connection failures and the development of fatigue cracks in tubular members, is highly dependent on the dynamic characteristics of both the damper and the structure. In addition, the expected amplitude of vibration should be taken into account when designing damping devices for a given structure because damping is a function of both frequency and amplitude of structural motion. The practice of optimizing the damper design for specific structures, however, is very limited, and the same number and configuration of dampers (with identical dynamic parameters) are universally used in many structures, irrespective of their span length and weight. To achieve optimal damping performance for highway sign trusses, this paper investigates the dynamic behavior of dampers through a series of laboratory experiments and a simplified analytical model. The testing and analysis results suggest significant improvement in vibration response and fatigue performance of structures over the currently installed dampers by implementing a few simple recommendations for damper selection.