Thermal-Induced Fatigue of Overhead Truss Structures

Abstract

Dynamic messaging signs (DMS) are found in operation over freeways, expressways, and other major intersections and provide information to travelers. If the DMS structure fails, then pedestrians and motorists can be harmed. An unstudied contributor to the reduced operation life of DMS structures is yearly thermal cycles. During the winter and summer times, the thermal variations tend to be large in range, in which daily and seasonal temperature variation can contribute to cyclic-caused fatigue. The objective of this study is to analyze thermal-induced fatigue life of highway overhead support structures. Field monitoring, mathematical analysis, and finite-element modeling were employed to perform the objective. The finite-element modeling extends to two different type of connection (slotted gusset welded joints and tube-to-tube welded joints) and two different materials (structural steel and aluminum alloy). Based on the estimated fatigue life for the overhead truss structures, the structural steel slotted gusset welded connection type provides larger fatigue life than other cases.