1. A. T. Tankut Middle East Technical University, Turkey
68th SOEAA, Florianapolis, Brazil SEISMIC REHABILITATION OF RC STRUCTURES- AN OVERVIEW
A. T. Tankut
Middle East Technical University, Turkey

2. A NOTE ON THE CONTENTS
Initial intention was to discuss the philosophy behind seismic strengthening under the title “Seismic Rehab Strategy”
Considering the audience consisting of various disciplines, policy was changed.
Basic concepts and methods that may interest the audience will be reviewed.

3. OUTLINE Introduction and Basic Concepts Common Structural Systems
Rehabilitation Techniques Available
An Innovative Rehabilitation Technique

4. INTRODUCTION & BASIC CONCEPTS

5. INTRODUCTION “Earthquake” is a natural phenomenon
It is tolerable in countries where the people and the built environment are prepared for it;
It leads to a disaster in countries where the built environment and the people are not prepared for it.

6. INTRODUCTION “Earthquake Preparedness” consists of
Disaster Management (post-quake) – Search & rescue, sheltering, food, medical care etc. (Easy but not effective)
Risk Management (pre-quake) – Safe towns, safe structures, well educated public, well trained engineers, effective financing etc. (Hard but very effective)

7. INTRODUCTION
Seismic rehab of the existing bldg stock is the most critical item in risk mitigation.
A huge unsafe building stock exists.
A systematic assessment reveals that
- A small number is seismically safe,
- A certain portion is to be demolished,
- The majority is to be strengthened.

8. COMMON STRUCTURAL SYSTEM

9. COMMON TYPE OF STR
Reinforced concrete framed building structures are common in southeast Europe including Turkey.
Partitioning walls of hollow brick masonry make the structure infilled frame and changes its behaviour.

10. COMMON DEFICIENCIES
Of these RC framed building structures with hollow brick masonry infill,
* Low-rise (12 floor) are not vulnerable;
* High-rise (> 1012 floor) buildings are carefully designed and constructed;
* Mid-rise (38floor) bldgs of inferior material, poor design and construction quality present the major problem.

11. COMMON DEFICIENCIES Mid-rise buildings of inferior quality
Constitute the majority in small towns;
Collapse in the pancake mode; thus
Are responsible from the high number of human losses and severe damage,
Are generally too good for demolition;
Are greatly in need of rehabilitation.

12. COMMON DEFICIENCIES Common deficiencies of such buildings:
Insufficient lateral stiffness
Deficient reinforcement detailing
Deficient design practice
Poor concrete
poor workmanship etc.

13. REHABILITATION TECHNIQUES AVAILABLE

14. Member Strengthening Techniques

15. COLUMN STRENGTHENING Methods for column strengthening
For axial load and bending Reinforced concrete jacketing
For axial load only Steel jacketing
For concrete strength/lap splice - CFRP confinement

16. BEAM STRENGTHENING Methods for beam strengthening
For bending Additional layer with new steel
- CFRP applications to the same effect
For shear
- External clamps

17. JOINT STRENGTHENING Methods for joint strengthening
For shear Diagonal steel/CFRP dovels - External clamps Confining devices

18. SLAB STRENGTHENING Method for slab strengthening
For diapragm action Additional layer with new steel

19. Sysyem Behaviour Improvement Techniques

20. SYSTEM IMPROVEMENT Devices reducing seismic loads Base isolation
Active / passive control
Smart structures
Dampers
Energy absorbers etc.

21. SYSTEM IMPROVEMENT Lateral stiffness increasing elements
Cast-in-place reinf conc infilled frames
Masonry infills, reinforced with high strength precast concrete panels
Steel cross bracing
Post tensioning
External rigid frame to support the str

22. AN INNOVATIVE REHABILITATION TECHNIQUE

23. INTRODUCTION The basic question:
Cast-in-place reif conc infilled frame technique is suitable for post-quake repair of the evacuated buildings; but not for pre-quake rehabilitation of the buildings still in use.
Suitable techniques should be developed.

24. THE CHALLENGE To develop a rehabilitation method,
Suitable for the common building type (Hollow brick infilled RC frame)
Practical & economical, and above all
Occupant friendly (no more disturbance than an ordinary painting job)

25. THE ANSWER The answer is OFR (occupant friendly rehab)
To reinforce existing masonry infill wall with epoxy bonded PC panels, which are,
- Light enough to be handled by two
- Small enough to go through doors
- Relatively thin, 40~50 mm (high str)
- Connected to infill wall by epoxy, and
to frame by epoxy bonded dowels

26. EXPERIMENTAL WORK

27. TEST FRAMES 1/3 scale, one-bay, two-storey inferior quality RC frames,
(representing the actual practice)
- Strong beam-weak column
- Insufficient confinement
- Low quality concrete (C13~C16)

28. REFERENCE

29. STRENGTHENED (SQUARE)

30. REFERENCE

31. STRENGTHENED (SQUARE)

32. INTERPRETATION Significantly improved performance:
Increased load carrying capacity
Increased initial & final stiffness
Delayed strength degradation
Decelerated stiffness degradation
Better ductility
Much higher energy dissipation

33. PERFORMANCE IMPROVEMENT
Relative to masonry Relative to
infilled frame bare frame
Lateral load capacity 2.5 times  15 times
Lateral stiffness  3 times  20 times
Ductility  2 times  0.2 times
Energy dissipation  3 times  60 times

34. CONCLUSION

35. CONCLUSION
PC panel technique is a very effective and practical seismic rehabilitation method for existing buildings.
Leads to a significant improvement in seismic performance
Is easily applied to buildings in use with minimal disturbance
Is cost effective (Comparable to cast-in-place RC infills)

36. THANKS
for your attention...

37. A. T. Tankut Middle East Technical University, Turkey
68th SOEAA, Florianapolis, Brazil SEISMIC REHABILITATION OF RC STRUCTURES- AN OVERVIEW
A. T. Tankut
Middle East Technical University, Turkey