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

1. Seismic Retrofit:
Criteria, Weakness & Methods
by
Paul W. McMullin, SE, PhD
CRSA Green Brains Seminar
June 26, 2008

2. Outline
Performance
Weaknesses
Options
SDEDC (1994)
Seismic Retrofit

3. Life Safety Through the Eyes of an SE
GET PEOPLE
OUT THE
DOOR ALIVE
Seismic Retrofit

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. Life Safety Through the Eyes of an SE
Structural Code generally
does not consider:
Building economics
Business interruption losses
Sustainability
Seismic Retrofit

6. Building State After a Major Earthquake
Northridge Earthquake
Magnitude 6.7
Estimated Economic
Loss $49.3 billion
PEER (2000)
Seismic Retrofit

7. Building State After a Major Earthquake:
Northridge
SDEDC (1994)
Seismic Retrofit

8. Building State After a Major Earthquake:
Northridge
FEMA (2000)
Seismic Retrofit

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. 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. 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. Common Damage
Seismic Retrofit

13. Common Damage
Seismic Retrofit

14. Common Weaknesses: Masonry
Unreinforced Masonry:
Everything
Reinforced Masonry:
(generally perform well)
Under-reinforced
Ungrouted cells
Connections
Seismic Retrofit

15. Common Weaknesses: Concrete
Ductility is big issue:
Continuous beam
reinforcing
Hoop spacing
Lap splices
Under-reinforced (primary)
Seismic Retrofit

16. Common Weaknesses: Concrete
EQE (1999 Taiwan)
Seismic Retrofit

17. Common Weaknesses: Timber
DETAILING
Cross grain bending
Continuity
Shear transfer
Undersized Elements
Nail pattern too far apart
Seismic Retrofit

18. Common Weaknesses: Steel
Constraint
Full penetration welds
Redundancy
Material Over strength
FEMA (2000)
Seismic Retrofit

19. Common Weaknesses: Steel
Constraint
Full penetration welds
Redundancy
Material Over strength
FEMA (2000)
Seismic Retrofit

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. Retrofit Options: Masonry
Seismic Retrofit

22. Retrofit Options: Masonry
Seismic Retrofit

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. Retrofit Options: Timber
Structural Panel overlay
Increased nailing
Sheet metal blocking
Steel Connectors (Simpson is
our friend)
Seismic Retrofit

25. Retrofit Options: Timber
Seismic Retrofit

26. Retrofit Options: Steel
Cover Plates
Shear Walls (steel or
concrete)
Braced Frames out of
Moment Frames
Seismic Retrofit

27. Preguntas?
Questions?
Seismic Retrofit