Development of Non-Fracture Critical Steel Box Straddle Caps

Steel box straddle caps are commonly utilized in congested urban environments when intersecting roadways do not permit conventional piers. The high strength-to-weight ratio of steel makes the straddle caps efficient from a construction and performance perspective; however, the members are categorized as fracture-critical, necessitating more stringent design requirements and biennial hands-on inspections—creating significant long-term costs. Researchers will develop details that allow the straddle box caps to be classified as redundant members, removing the fracture-critical designation on the caps. The study will not only target on new construction, but also evaluate methods of retrofitting existing caps to develop desired redundancy. Researchers will investigate the use of prestressing tendons/bars to provide redundancy to the steel box straddle caps. The methods of research include full-scale laboratory testing consisting of fatigue loading to initiate cracks and fracture tests under static loading on post-tensioned straddle box caps. Computational models will be used to develop a comprehensive design methodology for system redundant straddle caps that are non-fracture-critical. The systems developed will create significant benefits in both the life-cycle economy and long-term performance of steel straddle caps.


  • English


  • Status: Completed
  • Funding: $989286
  • Contract Numbers:


  • Sponsor Organizations:

    Texas Department of Transportation

    125 E. 11th Street
    Austin, TX  United States  78701-2483
  • Managing Organizations:

    Texas Department of Transportation

    125 E. 11th Street
    Austin, TX  United States  78701-2483
  • Project Managers:

    Dassi, Martin

  • Performing Organizations:

    Center for Transportation Research

    3925 W. Braker Lane
    Austin, TX  United States  78759
  • Principal Investigators:

    Helwig, Todd

  • Start Date: 20190709
  • Expected Completion Date: 20230531
  • Actual Completion Date: 20230531

Subject/Index Terms

Filing Info

  • Accession Number: 01713067
  • Record Type: Research project
  • Source Agency: Texas Department of Transportation
  • Contract Numbers: 0-7012
  • Files: RIP, STATEDOT
  • Created Date: Jul 30 2019 3:38PM