New Methods for Improving Load Rating of Existing Steel Bridges for Torsional Buckling

There are hundreds of steel bridges in Oregon that are in good condition and have performed well over extended lives. However, newly implemented rating checks for lateral-torsional buckling are now resulting in low rating factors that could require load posting for hundreds of bridges. Most of these steel bridges are simply supported steel stringers with either timber or corrugated metal decks and the bridges are located throughout the state. These bridges rated adequately using prior load rating methods, but recent updating of the load ratings using LRFR now produces very low rating factors for positive moment at mid-span. The main difference between the old and new methods is that lateral torsional buckling (LTB) controls the moment capacity and this was not checked in the old rating. There are cases where the rating factor is zero meaning the bridge cannot carry any truck load. Oregon Department of Transportation (ODOT) load rating engineers have tried to develop analytical tools based on limited prior research but many bridges still have low ratings and require load posting.

Language

• English

Project

• Status: Active
• Contract Numbers:

  SPR 874

• Sponsor Organizations:

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Managing Organizations:

  Oregon Department of Transportation

  355 Capital St NE MS42
  Salem, Oregon  United States  97301
• Project Managers:

  Silverman, Sean

• Performing Organizations:

  Oregon State University, Corvallis

  School of Civil and Construction Engineering
  101 Kearney Hall
  Corvallis, OR  United States  97331-2302
• Principal Investigators:

  Higgins, Christopher

• Start Date: 20230901
• Expected Completion Date: 20250831
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Buckling; Load factor; Methodology; Steel bridges; Torsional strength
• Geographic Terms: Oregon
• Subject Areas: Bridges and other structures; Highways;

Filing Info

• Accession Number: 01964193
• Record Type: Research project
• Source Agency: Oregon Department of Transportation
• Contract Numbers: SPR 874
• Files: RIP, STATEDOT
• Created Date: Aug 28 2025 1:51PM