LoadPath PDH — PE/NICET supplemental PDH (not FHWA/NBIS refresher training).

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Load RatingOnline self-study

LRFR Rating Factor Equation and Load Factors

1 PDH · about 60 minutes · Course no. BR-L01 · 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.

Load and Resistance Factor Rating (LRFR) is the load rating method in Section 6, Part A of the AASHTO Manual for Bridge Evaluation (MBE). FHWA considers it the preferred method, and since October 1, 2010 FHWA policy has called for bridges designed by LRFD to be load rated by LRFR. This course takes apart the general load-rating equation term by term, shows where each load factor comes from in MBE Table 6A.4.2.2-1 and the legal and permit tables, explains the optional condition and system factors and their 0.85 floor, and works through numerical examples showing how inventory, operating, legal and permit results are read and used.

⬇ Download study guide (PDF)

Learning objectives

  • Write the LRFR rating factor equation
  • Select design, legal and permit load factors
  • Apply condition and system factors
  • Interpret inventory and operating results

Outline

  1. Why a rating factor and not a design check
  2. The general load-rating equation
  3. Load factors from MBE Table 6A.4.2.2-1
  4. Condition and system factors
  5. Part A — The denominator: live load and dynamic load allowance
  6. Part B — Inventory and Operating in the design-load rating
  7. Part C — Legal-load factors and their calibration
  8. Part D — Permit-load factors
  9. Part E — Choosing limit states for each level
  10. Part F — Worked example 1: design-load rating of a steel girder
  11. Part G — Worked example 2: the same girder after deterioration
  12. Part H — Worked example 3: the 0.85 floor on a nonredundant bridge
  13. Part I — Worked example 4: legal-load rating and posting arithmetic
  14. Part J — Worked example 5: a routine permit check
  15. Part K — Reading and using rating results
  16. Part L — Common LRFR errors
  17. Part M — Reviewer's checklist for an LRFR rating
  18. Part N — Summary
  19. Open the course (24 screens, 2 knowledge checks)
  20. Final quiz — 10 questions, 70% to pass

References

  1. AASHTO, The Manual for Bridge Evaluation, 3rd Edition, 2018 (with interim revisions)
  2. AASHTO, LRFD Bridge Design Specifications, 9th Edition, 2020