Mitigating Signal Mast Arm Fatigue

In the Best Thing I Saw This Week #11 Valmont has developed and studied a device that helps reduce the "galloping" and oscillations of mast arms on traffic signal poles. The current AASHTO fatigue design recommendations to deal with long mast arms and high wind forces has led to very large pole designs. In urban areas where space is constrained and where every inch is important to ADA accessibility, finding ways to reduce pole size and costs are a welcome relief. The device called the "Mitigator" is a cylinder with a tension spring and reciprocating mass assembly that counters the oscillating effects that mast arms experience in wind or with truck passage. It can nicely be placed behind traffic signal heads at the end of a mast arm. The dampening effects are significant and they have completed research at the University of Connecticut and had devices field tested in Utah (UDOT), Colorado (CDOT), Nevada (NVDOT), Arizona (AZDOT), City of Hartford, CT, City of Seattle, WA and City of Omaha, NE. Vibration reductions in the 85-90% range have been observed.

Carl Macchietto of Valmont has been actively involved in the testing work and James Ford presented on their work in Hartford at the Northeastern District ITE Meeting this spring when I first heard of the device. Work has been going on in this area for some time. I have encouraged Carl and Kellie Koedel to publish their work and we should be seeing it soon. Any research that uses a "pluck" and "poing" tests to mitigate "galloping" is pretty cool. Not to mention a cost effective way to reduce signal pole fatigue and extend their life cycle.