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Load RatingOnline self-study

Gusset Plate Load Rating

1 PDH · about 60 minutes · Course no. BR-L05 · Instructor: Michael Craig, PE

About the instructor

Michael Craig, PE is Senior Vice President and Southeast Director at Strinteg Corporation, leading bridge inspection and structural engineering across eight states and Puerto Rico. In 27+ years he has inspected over 4,000 structures and completed 3,000+ load ratings and 160+ load tests. He has managed repair and preservation design for complex bridges, including cable-stayed bridges. He holds PE licenses in twelve states, DC and Puerto Rico, SPRAT Level 1, and FAA Part 107 credentials.

Before 2007, most truss load ratings checked members and assumed the connections were stronger than the members they joined. The collapse of the I-35W bridge in Minneapolis on August 1, 2007, which the National Transportation Safety Board attributed to undersized gusset plates, ended that assumption. This course explains how gusset plate rating became a national priority, the five minimum resistance checks in the FHWA guidance document FHWA-IF-09-014 (fasteners, shear yielding and fracture, Whitmore compression, Whitmore tension, block shear), how to handle section loss and plate buckling, and what the later NCHRP Project 12-84 research changed. Equations and factors are taken from FHWA-IF-09-014 and from FHWA TechBrief FHWA-HRT-14-063, which summarizes NCHRP 12-84. Example numbers are illustrative teaching values unless a source is named.

⬇ Download study guide (PDF)

Learning objectives

  • Explain why gusset rating became a priority
  • List gusset limit states
  • Apply FHWA guidance resistance checks
  • Account for section loss and plate buckling

Outline

  1. Why gusset plate rating became a priority
  2. The five minimum checks in FHWA-IF-09-014
  3. Compression: the Whitmore section and the equivalent column
  4. Tension checks and block shear
  5. Fasteners: rivets, bolts and plate bearing
  6. What NCHRP Project 12-84 changed
  7. How the resistance factors were calibrated
  8. Section loss, inspection data and multilayer plates
  9. Worked example (illustrative): shear and Whitmore checks
  10. A practical rating workflow
  11. LRFR, LFR and owner policy
  12. Common pitfalls
  13. Retrofit and posting decisions
  14. Summary
  15. Worked example (illustrative): tension diagonal
  16. Glossary
  17. Reviewer's checklist for a gusset plate rating
  18. Open the course (23 screens, 2 knowledge checks)
  19. Final quiz — 10 questions, 70% to pass

References

  1. FHWA, Load Rating Guidance and Examples for Bolted and Riveted Gusset Plates in Truss Bridges, FHWA-IF-09-014, 2009
  2. AASHTO, The Manual for Bridge Evaluation, 3rd Edition, 2018 (with interim revisions)
  3. FHWA, Guidelines for Design and Rating of Gusset-Plate Connections for Steel Truss Bridges (TechBrief), FHWA-HRT-14-063, August 2014
  4. FHWA Technical Advisory T 5140.29, Load-Carrying Capacity Considerations of Gusset Plates in Non-Load-Path-Redundant Steel Truss Bridges, January 15, 2008
  5. NTSB, Collapse of I-35W Highway Bridge, Minneapolis, Minnesota, August 1, 2007, Highway Accident Report NTSB/HAR-08/03, 2008
  6. NCHRP Web-Only Document 197, Guidelines for the Load and Resistance Factor Design and Rating of Riveted, Bolted, and Welded Gusset-Plate Connections for Steel Bridges (NCHRP Project 12-84)