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Load RatingOnline self-study

Rating Deteriorated Members: Section Loss and Condition Factors

1 PDH · about 60 minutes · Course no. BR-L04 · 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.

Most bridges that need a careful load rating are not new. They have corroded flanges, perforated webs, spalled and delaminated concrete, exposed and section-reduced reinforcing, and bearings that no longer work as designed. This course covers how a load rating engineer turns inspection findings into the section properties used in an LRFR rating, how the condition factor (MBE Article 6A.4.2.3) and the system factor (MBE Article 6A.4.2.4) enter the capacity term, why those two factors must not be used to count the same deterioration twice, and how to document assumptions so that a reviewer, and the next engineer, can follow the rating. Factor values in this course are taken from the AASHTO Manual for Bridge Evaluation (MBE) tables as reproduced in AASHTO's published errata and in FHWA's Steel Bridge Design Handbook. Worked-example numbers are illustrative teaching values unless a source is named.

⬇ Download study guide (PDF)

Learning objectives

  • Translate inspection data into section properties
  • Apply the condition factor correctly
  • Avoid double-counting deterioration
  • Document assumptions for reviewers

Outline

  1. Why deterioration belongs in the rating
  2. The condition factor φc (MBE 6A.4.2.3)
  3. The system factor φs (MBE 6A.4.2.4)
  4. From inspection notes to section properties: steel members
  5. From inspection notes to section properties: concrete and prestressed members
  6. Avoiding double-counting deterioration
  7. Worked example: a corroded rolled-beam bridge
  8. Worked example: a two-girder welded bridge and the 0.85 floor
  9. When does deterioration warrant a new rating?
  10. Documenting assumptions for reviewers
  11. Worked example: a prestressed beam with broken strands
  12. Element-level data, condition states and the BIRM
  13. Common pitfalls and quick answers
  14. How deterioration flows through the rating levels
  15. Putting it together: a five-step workflow
  16. Open the course (21 screens, 2 knowledge checks)
  17. Final quiz — 10 questions, 70% to pass

References

  1. AASHTO, The Manual for Bridge Evaluation, 3rd Edition, 2018 (with interim revisions)
  2. FHWA, Bridge Inspector's Reference Manual (BIRM), FHWA-NHI-12-049, 2012 (as revised)
  3. FHWA, Steel Bridge Design Handbook, Chapter 18: Load Rating of Steel Bridges, FHWA-HIF-16-002 Vol. 18, 2015
  4. AASHTO, Manual for Bridge Evaluation, Third Edition, Errata (November 2021)
  5. Maine DOT, Load Rating Guide, April 2015
  6. West Virginia DOH, Bridge Load Rating Manual, 2023