Evaluation of Fatigue Resistance of Multi-sided Sign and Traffic Signal Structures

摘要

Over the past two decades fatigue failure of cantilevered highway sign and traffic signal structures are increasingly being reported around the United States, primarily due to wind induced oscillations. For aesthetic reasons many of these structures are built with multisided tubular sections with sharp corners. Fatigue performance of fillet-welded tube-to-end plate connections in multi-sided sign/signal structures were evaluated by laboratory testing and parametric finite element analyses (FEA). Seven full size galvanized sign/signal structure specimens having eight sided cross section were fatigue tested under constant amplitude loading simulating wind induced aero-elastic galloping oscillation. Fatigue cracking in multi-sided sections mostly initiate at the bend corners of tube-to-end plate welded connection, and may appear early in service. Flexibility of the end plate, the number of sides, and the corner bend radius are the important parameters that affect fatigue resistance of multi-sided tubular structures. The existing specification does not address the effects of the connection geometry on their fatigue design. The experimental and analytical studies established the fatigue design provisions of tube-to-end plate connections in multi-sided sign and signal structures.