Experimental Validation of the AASHTO Natural Wind Fatigue Design Specifications for Cantilevered Sign Support Structure Anchor Bolts

A cantilevered sign support structure failed, which was attributed to fatigue fracture of the anchor bolts. The failed structure was designed before the publication of the AASHTO fatigue provisions. The structure was replaced with a similar arrangement but designed using the AASHTO fatigue provisions. It was equipped with a double-nut-moment joint to concrete foundation using a 31.75-mm (1.25-in.) thick, 889-mm (35-in.) diameter base plate and eight galvanized 38.1-mm (1.5-in.) diameter bent anchor bolts. Significant clearance discrepancies between the base plate and the foundation for each of the anchor bolts existed because of topographical limitations. Experimental evaluation on the fatigue behavior attributable to natural wind was conducted on the anchor bolt attachments for validation of the AASHTO fatigue provisions. The results of the study indicated an irregular distribution of stress ranges between anchor bolts, with a portion having stress ranges greater than the values calculated using the AASHTO standards as well as the constant-amplitude fatigue limit of the anchor bolt connection detail. (C) 2014 American Society of Civil Engineers.