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SeismicOnline self-study

Seismic Retrofit of Existing Bridges

1 PDH · about 60 minutes · Course no. BR-E02 · 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 of the nation's bridges were designed before modern seismic provisions existed. FHWA's Seismic Retrofitting Manual for Highway Structures: Part 1, Bridges (FHWA-HRT-06-032, January 2006, by Buckle, Friedland, Mander, Martin, Nutt and Power) gives owners a performance-based process for deciding which existing bridges need attention, how to evaluate them, and what to do about it. This course follows that process: the lessons of past earthquakes, the two-level ground motion and performance framework, service life and importance, seismic hazard levels and seismic retrofit categories, screening and prioritization with the indices method, evaluation methods from simple capacity checks to nonlinear analysis, the vulnerable details that cause most failures, and the retrofit approaches and measures available, including seat extensions, restrainers, column jackets and foundation work, with cost data the manual reports from California.

⬇ Download study guide (PDF)

Learning objectives

  • Identify vulnerable details
  • Explain screening and evaluation
  • Select retrofit measures
  • Prioritize retrofit

Outline

  1. Why retrofit, and what history taught
  2. Performance-based framework: ground motions, service life and importance
  3. Seismic hazard levels and retrofit categories
  4. Lower-level event screening
  5. Screening and prioritization
  6. Evaluation methods
  7. Vulnerable details
  8. Retrofit approaches
  9. Retrofit measures
  10. Column jackets in detail
  11. Restrainers, seats and the load path
  12. Costs and program management
  13. Open the course (18 screens, 2 knowledge checks)
  14. Final quiz — 10 questions, 70% to pass

References

  1. FHWA, Seismic Retrofitting Manual for Highway Structures, FHWA-HRT-06-032, 2006