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原文传递 Re-tightening the Large Anchor Bolts of Support Structures for Signs and Luminaires.

题名：	Re-tightening the Large Anchor Bolts of Support Structures for Signs and Luminaires.
作者：	Chen, A.; Schaeffer, C.; Zhang, Y.; Phares, B.; Shafei, B.; Yang, M.; Lin, Z.; Paudel, S.
关键词：	Overhead traffic signs, Structural supports, Traffic signals, Anchor bolts, High mast lighting, Structural parts, Nuts (Fasteners), High-Mast Light Tower (HMLT), Recommendation, Numerical analysis, American Assocation of State Highway Transportation Officials (AASHTO)
摘要：	Many state Departments of Transportation (DOT) across the US, including MnDOT, are experiencing problems associated with loose anchor bolts used in support structures (e.g., overhead signs, high-mast light tower (HMLT), and tall traffic signals). Specifically, MnDOT inspection crews have found loose nuts at most anchor bolt locations, even at some newly installed signs. Many of these nuts became loose in less than two years, even after being tightened by the maintenance crew following current recommended procedures. This situation has placed great strain on the resources from the districts鈥?maintenance group and also causes concerns related to inspection frequency and public safety. This project investigated causes of the loose anchor bolts and proposes solutions based on site surveying, field monitoring, laboratory study, and numerical analysis. The research team found that the tightening process proposed in AASHTO鈥檚 specification is a sufficient alternative for MnDOT, though it requires modification in three key areas: defining snug-tight, accounting for grip length, and recommending verification procedures. The research team quantified snug-tight values, and defined the relationship between torque, tension, and nut rotation through empirical constants. Recommendations are made for a new specification for MnDOT structures.
报告类型：	科技报告