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Seismic retrofit methods


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Summary of seismic retrofit criteria, typical weaknesses of older buildings, and retrofit methods. Geared for architects.

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Seismic retrofit methods

  1. 1. Seismic Retrofit: Criteria, Weakness & Methods by Paul W. McMullin, SE, PhD CRSA Green Brains Seminar June 26, 2008
  2. 2. Outline Performance Weaknesses Options SDEDC (1994) Seismic Retrofit
  3. 3. Life Safety Through the Eyes of an SE GET PEOPLE OUT THE DOOR ALIVE Seismic Retrofit
  4. 4. Life Safety Through the Eyes of an SE The purpose of this code is to establish the minimum requirements to safeguard the public health, safety and general welfare… (IBC 2006, 101.3) Seismic Retrofit
  5. 5. Life Safety Through the Eyes of an SE Structural Code generally does not consider: Building economics Business interruption losses Sustainability Seismic Retrofit
  6. 6. Building State After a Major Earthquake Northridge Earthquake Magnitude 6.7 Estimated Economic Loss $49.3 billion PEER (2000) Seismic Retrofit
  7. 7. Building State After a Major Earthquake: Northridge SDEDC (1994) Seismic Retrofit
  8. 8. Building State After a Major Earthquake: Northridge FEMA (2000) Seismic Retrofit
  9. 9. Performance Based Seismic Design: Basics Next generation seismic design methodology Originally developed by FEMA for existing buildings Applicable for new design Considers each element’s energy dissipation capacity Seismic Retrofit
  10. 10. Performance Based Seismic Design: Pairing Target Building Performance Levels Operational Performance Performance Level (1-B) Performance Level (5-E) Life Safety Performance Immediate Occupancy Collapse Prevention Level (3-C) Level (1-A) Once every 100 years a b c d Once every 250 years e f g h Hazard Level Earthquake Once every 500 years i j k l Once every 2500 years m n o p Seismic Retrofit
  11. 11. Performance Based Seismic Design: Levels & Acceleration Performance levels Acceleration Options Operational Typical Immediate Occupancy 50%/50 (1/100 year) Life Safety (IBC) 20%/50 (1/250 year) Collapse Prevention 10%/50 (1/500 year) 2/3 of 2%/50 (IBC) 2%/50 (1/2500 year) Any probability between those listed above Seismic Retrofit
  12. 12. Common Damage Seismic Retrofit
  13. 13. Common Damage Seismic Retrofit
  14. 14. Common Weaknesses: Masonry Unreinforced Masonry: Everything Reinforced Masonry: (generally perform well) Under-reinforced Ungrouted cells Connections Seismic Retrofit
  15. 15. Common Weaknesses: Concrete Ductility is big issue: Continuous beam reinforcing Hoop spacing Lap splices Under-reinforced (primary) Seismic Retrofit
  16. 16. Common Weaknesses: Concrete EQE (1999 Taiwan) Seismic Retrofit
  17. 17. Common Weaknesses: Timber DETAILING Cross grain bending Continuity Shear transfer Undersized Elements Nail pattern too far apart Seismic Retrofit
  18. 18. Common Weaknesses: Steel Constraint Full penetration welds Redundancy Material Over strength FEMA (2000) Seismic Retrofit
  19. 19. Common Weaknesses: Steel Constraint Full penetration welds Redundancy Material Over strength FEMA (2000) Seismic Retrofit
  20. 20. Retrofit Options: Masonry Unreinforced Masonry Post Tensioning Adding Perforations Vertical Wall Coring Slotting Shotcrete Fiber Reinforced Plastics (FRP) Reinforced Masonry Shotcrete FRP Seismic Retrofit
  21. 21. Retrofit Options: Masonry Seismic Retrofit
  22. 22. Retrofit Options: Masonry Seismic Retrofit
  23. 23. Retrofit Options: Concrete Shear Walls Grade Beams Steel or FRP Wrap of columns/ beams Application to flat surface Concrete jacketing (steel fiber reinforced) Seismic Retrofit
  24. 24. Retrofit Options: Timber Structural Panel overlay Increased nailing Sheet metal blocking Steel Connectors (Simpson is our friend) Seismic Retrofit
  25. 25. Retrofit Options: Timber Seismic Retrofit
  26. 26. Retrofit Options: Steel Cover Plates Shear Walls (steel or concrete) Braced Frames out of Moment Frames Seismic Retrofit
  27. 27. Preguntas? Questions? Seismic Retrofit