Flexural Resistance of I-Sections for Skewed and/or Curved Steel I-Girder Bridges

Currently, in the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications (BDS), the nominal flexural resistance of I-girder bridges that are (1) kinked (chorded) and continuous, (2) horizontally curved, or (3) straight with supports skewed more than 20 degrees from normal is conservatively not allowed to exceed first yield at the strength limit state for the following reasons: Such bridges typically experience significant differential vertical deflections at the cross-frames resulting in larger cross-frame forces in the elastic range. As interior-pier sections yield and begin to lose stiffness and shed their load, the forces in the adjacent cross-frames will increase. There is currently no established procedure to predict the resulting increase in the forces without performing a refined nonlinear analysis. In horizontally curved bridges and severely skewed straight bridges with discontinuous cross-frames, significant lateral flange bending effects can occur. The resulting lateral bending moments and stresses are amplified in the bottom compression flange adjacent to the pier as the flange deflects laterally. There is currently no means to accurately predict these amplification effects as the flange is also yielding. Skewed supports also result in twisting of the girders, which is not recognized in plastic-design theory. The relative vertical deflections of the girders create eccentricities that are also not recognized in the theory. Research is needed to address these load and resistance factor design (LRFD) issues to help state departments of transportation (DOTs) achieve more efficient designs and recognize improved accuracy in load ratings for existing bridges. OBJECTIVE: The objective of this project is to develop a methodology to determine the nominal flexural resistance beyond first yield at the strength limit state in I-girder bridges that are (1) kinked (chorded) and continuous, (2) horizontally curved, or (3) straight with supports skewed more than 20 degrees from normal. 

• Record URL:
  • http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=5671
• Supplemental Notes:
  • Contract to a Performing Organization has not yet been awarded.

Language

• English

Project

• Funding: $500,000.00
• Contract Numbers:

  Project 12-128

• 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

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Project Managers:

  Abu-Hawash, Ahmad

• Start Date: 20250114
• Expected Completion Date: 0
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Bridge design; Curved bridges; Flexural strength; Flexure; Girder bridges; Skew bridges; Webbing
• Subject Areas: Bridges and other structures; Design; Highways;

Filing Info

• Accession Number: 01919269
• Record Type: Research project
• Source Agency: Transportation Research Board
• Contract Numbers: Project 12-128
• Files: TRB, RIP
• Created Date: May 21 2024 5:15PM