TIGHTENING PROCEDURES FOR LARGE-DIAMETER ANCHOR BOLTS

Recent failures of cantilever overhead sign structures in Michigan and elsewhere, coupled with the absence of standards for tightening methods for the double-nut system used with large-diameter anchor bolts in similar structures in Texas have been the motivation for this study. Practices of various field offices were reviewed, a literature study was performed, and both laboratory studies and field studies were performed. Three questions were raised: How tight do the anchor bolt nuts need to be? What techniques and procedures are best suited for tightening? How can tightness best be inspected? Standards for tightening procedures for large-diameter anchor bolts are proposed. In current Texas Department of Transportation practice, the contractor is left to his or her own judgment concerning how tight to tighten the nuts on the double-nut anchor bolt system. Recent bolt failures in other states have raised concerns about nut tightening procedures. When the nuts of a double-nut system are not tightened sufficiently, fatigue loading, and even impact loading, can be factors in the performance of the bolts. Three full-size test specimens were built in the laboratory to evaluate tightening methods and the fatigue performance of the double-nut system used for anchorage of cantilever overhead sign structures (COSS) and on high mast illumination poles (HMIP). Analytical and numerical studies were performed to identify and study parameters affecting the stresses in the anchor bolts. Field studies were conducted to measure the wind-load induced anchor bolt reactions and stresses in one specimen of each type. This report details these studies and the findings.

• Supplemental Notes:
  • Published December 1996; resubmitted June 1997. Research study title: Tightening Procedures for Large-Diameter Anchor Bolts.
• Corporate Authors:

  Texas Transportation Institute

  Texas A&M University System, 1600 E Lamar Boulevard
  Arlington, TX  United States  76011

  Texas Department of Transportation

  Research and Technology Transfer Office, P.O. Box 5051
  Austin, TX  United States  78763-5051

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • JAMES, R W
  • Keating, P B
  • Bolton, R W
  • Benson, F C
  • Bray, D E
  • Abraham, R C
  • Hodge, J B
• Publication Date: 1997-6

Language

• English

Media Info

• Features: Appendices; Figures; Photos; References; Tables;
• Pagination: 206 p.

Subject/Index Terms

• TRT Terms: Aerodynamic force; Anchor bolts; Failure; Fatigue (Mechanics); Field studies; Guides to the literature; Impact loads; Laboratory studies; Lighting columns; Literature reviews; Loads; Sign supports; Signs; Standards; Stresses; Wind
• Uncontrolled Terms: Wind load
• Old TRIS Terms: Double-nut system; Fatigue loading; Impact loading; Sign structures; Tightening
• Subject Areas: Bridges and other structures; Highways; I20: Design and Planning of Transport Infrastructure;

Filing Info

• Accession Number: 00744892
• Record Type: Publication
• Report/Paper Numbers: FHWA/TX-98/1472-1F, Res Rept 1472-1F, TTI: 0-1472 Final Report
• Contract Numbers: Study 0-1472
• Files: TRIS, USDOT, STATEDOT
• Created Date: Jan 29 1998 12:00AM