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Development of the Guidance on the Tightening of Large Anchor Rods of Support Structures for Sign and Luminaires
Ist Teil von
Transportation research record, 2023-07, Vol.2677 (7), p.317-325
Ort / Verlag
Los Angeles, CA: SAGE Publications
Erscheinungsjahr
2023
Link zum Volltext
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Across the United States, various state Departments of Transportation (DOTs) are finding that the base anchor-rod nuts on critical support structures for overhead signs are coming loose. Retightening loose nuts imposes a significant drain on state DOT resources. In addition, the loosening of these nuts increases the failure risk of tall and overhanging structures. In many of the inspection engineer’s observed cases, anchor-rod nuts were loose immediately after installation. Even after tightening, it was found that anchor-rod nuts had consistently come loose just 2 years after retightening. The objective of this study was to evaluate the resistance to the loosening of anchor-rod tightening procedures proposed by Chen et al. and to develop improvements to the procedures based on stakeholder feedback. To achieve this objective, field deployment of the previously developed procedures was conducted on multiple sites. After field deployment, improvements to the Chen et al. procedure were investigated on a full-size laboratory specimen to ensure revisions did not affect connection performance. Overall, it was found that the pretension levels proposed by Chen et al. were effective, and the revised procedures only use torque, or force-controlled tightening, as opposed to displacement-controlled turn-of-nut.