Fatigue Performance of Groove-Welded Tube-to-End-Plate Connections in Highway Sign, Luminaire, and Traffic Signal Structures

Abstract

Fatigue performance of full penetration groove-welded tube-to-end-plate connections was evaluated by parametric studies verified by laboratory testing of full-scale galvanized cantilevered highway sign and 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 is governed by secondary out-of-plane bending stress, the magnitude of which depends on relative stiffness of the tube and end plate. In some groove-welded connections, the backing ring is welded to the tube wall, adding more variability in fatigue performance of the connection. Twenty-three full-size specimens composed of five configurations of the groove-welded connections were fatigue-tested under constant amplitude loading simulating wind-induced aeroelastic oscillations, such as galloping and vortex shedding, that are typically experienced in service. Variation in six parameters of the connection geometry were considered: diameter of tube, 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 a 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 configurations.

Advanced Analytical Methods for Fatigue Assessment of Ancillary Systems in Highway Bridges

“…These connections were tested experimentally in full size and they did not develop any fatigue cracking under both in-plane and out-of-plane loading scenarios. However, in all the tested specimens, the fatigue cracking occurred in other critical locations such as the tube-to-transverse-plate welds in the mast arm, the pole, and/or hand holes [22,24]. The connection between the side plate and the pole falls under the category of E`details in AASHTO specification having a CAFT of 2.6 ksi (18 MPa).…”

Application of strain-life fatigue-corrosion model for fillet-welded connections of sign support structures

“…However, there has been a fatigue concern on these connections, and it was determined that wind-induced cyclic fatigue stresses are the primary source of failure in welded connections according to previous investigations and published reports (Fisher et al, 1991; Foley et al, 2008; Gilani and Whittaker, 2000; John and Dexter, 1998; Kaczinski et al, 1998). Although the socket connections are cost-effective and easy to fabricate for support structures, a recent experimental research (Roy et al, 2011) reported that fillet-welded tube-to-transverse plate connection showed a poor fatigue resistance compared to other connection types (i.e. groove-welded connection).…”

Development of the Guidance on the Tightening of Large Anchor Rods of Support Structures for Sign and Luminaires

“…which were further improved by NCHRP web-only Document 176 (5). Note that the notation ''LTS-1'' will be used in this paper to refer to the first edition of AASHTO Load Factor and Resistance Design Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, including interim revisions up to 2020.…”

“…During the 1990s, fatigue provisions for SLTS structures were studied ( 3 ) and summarized in the National Cooperative Highway Research Program (NCHRP) Report 469 ( 4 ). The American Association of State Highway and Transportation Officials (AASHTO) developed specifications for SLTS structures based on NCHRP Report 469, which were further improved by NCHRP web-only Document 176 ( 5 ). Note that the notation “LTS-1” will be used in this paper to refer to the first edition of AASHTO Load Factor and Resistance Design Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals , including interim revisions up to 2020.…”