Investigation of fatigue in steel sign-support structures under diurnal temperature changes

Abstract Use of Dynamic Message Signs (DMSs) has significantly increased in roadway networks, owing to their unique capability to guide the traffic in real time. As a result, the structural performance assessment of the overhead trusses that hold DMSs has received a growing attention to ensure public safety and avoid traffic congestion. Despite the importance of this category of structures, there are only a few relevant studies available in the literature. The potential contribution of thermal stresses to damage, particularly in the joints of overhead truss structures, was among the critical aspects that had remained largely unknown. This was the motivation of the current study as the damage induced by temperature fluctuations can become significant, especially in the regions that experience large diurnal temperature changes. In the current study, two overhead DMS-support structures located in Iowa are selected for instrumentation and long-term monitoring. An array of vibrating-wire gauges are installed on these two DMS-support structures to understand the effects of diurnal temperature changes. Further to the analysis of collected field data, finite-element modeling is performed to evaluate the possibility of fatigue-induced damage. Based on the results obtained from this study, the DMS-support structures under consideration are found to provide a satisfactory performance under thermal loads. This strongly supports the recent transition from aluminum to steel overhead truss structures to avoid vulnerability to diurnal temperature changes.