Impact of Bolt Holes on the Performance of Steel Girders

The design and construction of steel girder bridges, most often, require the use of bolts to connect various components in the field. In some cases, bolt holes have to be located at critical locations such as the tension flange of a steel girder. The impact of these holes on the capacity and the performance of the steel girders are accounted for during design. The current American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications (BDS) Equation provides a limit on the maximum major-axis bending stress permitted on the gross area of steel girder flange, neglecting the loss of area due to holes in the tension flange. This equation is used in lieu of the 15 percent rule that had existed in previous editions of AASHTO design specifications, which allowed holes with an area less than or equal to 15 percent of the gross area of the flange to be neglected. However, for modern steels with yield-to-ultimate tensile strength ratio (Y/T ratio) higher than Grade 36 steel, the 15 percent rule was revised. The current provision is based on the yielding and fracture of axially loaded tension members as opposed to the yielding and fracture of tension flanges of flexural members. A refinement of the current provision may lead to improved design strength of steel I-girders, particularly for girders with longer spans where modern steels are employed. Research is needed to better understand the impact of tension flange holes on steel girder performance and possibly improve the current state-of-practice. The objective of this research is to conduct an analytical study on the impact of tension flange holes on the strength and ductility of composite steel I-girders and recommend modifications to existing compact steel I-girder design requirements, if needed. At a minimum, the research shall focus on Grade 50 and hybrid Grade HPS70W steel girders.


  • English


  • Status: Proposed
  • Funding: $250000
  • Contract Numbers:

    Project 10-127

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    Office of Planning, Environment and Realty (HEP)
    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Abu-Hawash, Ahmad

  • Start Date: 20240319
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01899009
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 10-127
  • Files: TRB, RIP
  • Created Date: Nov 13 2023 6:03PM