Fatigue performance of full penetration groove welded tube-to-end plate connections were evaluated by parametric studies verified by laboratory testing of full scale galvanized cantilevered highway sign/signal and high level luminaire structures. In the absence of sufficient experimental basis the fatigue resistance of this connection detail in the existing AASHTO specification is defined as Category E. Fatigue performance of tube-to-end plate connections in thin walled tubular structures are governed by secondary out-of-plane bending stress, the magnitude of which depends on relativestiffness of the tube and the end plate. In some groove welded connections, the backing ring is welded to the tube wall, adding more variability infatigue performance of the connection. Twenty three full size specimens comprising five different configurations of the groove welded connections were fatigue tested under constant amplitude loading simulating wind induced aero-elastic oscillations such as galloping and vortex shedding that aretypically experienced in service. Variation in six different parameters of the connection geometry were considered diameter and thickness of tube, thickness of end plate, diameter of end plate opening, number of anchor bolts, and height of backing ring. The research results demonstrated that with suitable combination of the geometric parameters, the constant amplitude fatigue threshold of the groove welded tube to end plate connections can exceed that of AASHTO fatigue category D for sections widely used in highway sign, luminaire and traffic signal structures. The local stress based approaches provided reasonable lower bound estimates of fatigue performance of the connection detail for different geometric configuration.
Abstract