Field Testing of Cantilevered Traffic Signal Structures under Truck-Induced Gust Loads

Changes in the AASHTO fatigue design equations for truck-induced gust loads have been made in recent years. However, there has not been any long-term field testing of cantilevered traffic signal structures to verify the design equations. In this study, two cantilevered traffic signal structures were monitored in field testing to determine the effects of truck-induced gust loads. Over 400 truck events were observed in the field, but only eighteen trucks produced a detectable effect on the cantilevered traffic signal structure. Interestingly, the truck-induced gusts caused a greater effect in the out-of-plane direction (same direction as traffic flow) instead of the in-plane direction that is included in the AASHTO Specifications. It was determined that overall natural wind gusts produce a larger response in cantilevered traffic signal structures than gusts produced by trucks passing beneath the signals.