The National Academies

NCHRP IDEA 20-30/IDEA 141 [Completed (IDEA)]

Reducing Fatigue in Wind-Excited Traffic Signal Support Structures using Smart Damping Techniques
[ NCHRP 20-30 (NCHRP-IDEA) ]

  Project Data
Staff Responsibility: Dr. Inam Jawed

This project developed a vibration absorbing system to reduce fatigue in traffic signal support structures exposed to excessive wind-induced vibration. A prototype smart vibration absorber was designed for installation onto a full-scale traffic signal support structure in the laboratory and free and forced vibration tests were conducted. Three different damper types were tested including a magneto-rheological (MR) fluid damper, an air damper, and a permanent magnet damper. The final prototype design used the permanent magnet damper because of the linear viscous damping achieved and simplified mechanics of the device. The prototype was evaluated by measuring damping level in the structure from free vibration response and measured steady state accelerations from forced vibration tests. Damping in the traffic signal support structure increased from 0.1% to 10.1% reducing free vibration time for the response to attenuate from over 5 minutes to just under 5 seconds. The system is expected to significantly reduce the wind-induced vibrations of traffic signal support structures, thereby reducing fatigue and increasing the safe life of the structure. For signal support owners, this  means that  fewer resources will need  to be committed to replacing and  repairing fatigued signal support structures. The retrofit would be applied to only those signal structures that exhibit vibration problems in the field, thus making the application and use of resources more efficient. The vibration absorber is relatively cheap, easy to install, and would provide savings in the form of increased life of the structure and supplemental information for signal support inspection. The monitoring capabilities would supplement visual inspections. Connecticut DOT’s Technology Transfer Center is helping in implementing the IDEA technology. (NTIS # PB2011-113455)  The contractor's final report is available.

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