Determination of U-Bolt Connection Fatigue Load Capacities in Overhead Sign Support Structures

Although they have appeared to perform well, the actual load capacities of U-bolt connections used in Iowa DOT steel overhead sign trusses are not known because they are used in ways that do not match available manufacturer data. A previous phase of this research initiated the determination of the load capacity of these U-bolt connections through limited laboratory tests and parametric studies performed on finite element (FE) models. It was noted at the conclusion of that work that additional laboratory tests should be performed on high-strength U-bolts subject to static loading in multiple directions and that the fatigue performance of the U-bolt connection should be investigated to understand the impact of repeated loads near the yield load. In order to resolve the concerns left from the previous phase of this research, this proposal is drafted with the goal of investigating the fatigue behavior of the U-bolt connections, evaluating the fatigue capacity of the U-bolt connections used on SOST, and validating the analytical results developed in the previous research. To achieve the proposed objectives, an eight-task 36-month research plan was developed, including conducting field monitoring, analytical simulation, and multiple stages of laboratory tests. The research results will assist engineers in effectively and efficiently designing overhead sign support sign structures without concern for the capacity and safety of the U-bolt connections.


  • English


  • Status: Active
  • Funding: $66650
  • Contract Numbers:


  • Sponsor Organizations:

    Iowa Department of Transportation

    800 Lincoln Way
    Ames, IA  United States  50010
  • Managing Organizations:

    Iowa Department of Transportation

    800 Lincoln Way
    Ames, IA  United States  50010
  • Project Managers:

    Clute, Khyle

  • Performing Organizations:

    Iowa State University, Ames

    Center for Transportation Research and Education
    2711 South Loop Drive, Suite 4700
    Ames, IA  United States  50010-8664
  • Principal Investigators:

    Phares, Brent

  • Start Date: 20221101
  • Expected Completion Date: 20240228
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01910231
  • Record Type: Research project
  • Source Agency: Iowa Department of Transportation
  • Contract Numbers: SPR-RE23(009)-8H-00
  • Files: RIP, STATEDOT
  • Created Date: Feb 27 2024 5:19PM