Bracing elements in structural system plays a vital role in the seismic behaviour of high rise buildings during earthquake. Many of the structural failures in buildings during strong earthquake shaking have indicated that sustainable strength and stable energy dissipation capability are most desirable to maintain inter story drifts and overall structural displacements within tolerable levels. So earthquake action brings a greater concern in the structural design of buildings which is situated in earthquake prone areas. Steel bracing are the common type which mainly used to resist the lateral loads acting during a seismic activity. Conventional types of lateral load resisting systems are concentrically-braced frames (CBFs) and eccentrically braced frames (EBF). Buckling Restrained Braces (BRB) are recent developed structural system which has a stable energy dissipation property. Main advantage of BRB is its ability to yield both in tension and compression without buckling, thus obtaining a stable hysteresis loop. The BRB brace placed in a concentric frame is termed as BRBF system.

1. BUCKLING RESTRAINED
BRACED FRAMES
Presented by
ASHLIN T V

2. INTRODUCTION
 The brace which attempts to inhibit buckling under
compression is called Buckling Restrained Brace
 Allow the building to withstand cyclical lateral
loadings, typically earthquake-induced loading
 Ability to yield both in tension and compression
without buckling
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

3. CBF
• Connection
failure
• Member fracture
• Loss of strength
and stiffness
SCBF
• Degradation of
brace capacity
and stiffness
• Brace fracture
• Undesirable
system response
BRBF
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering
NEED FOR A BETTER BRACE

4. FUNDAMENTALS OF BRB BEHAVIOUR
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Fig. 1 Behaviour of Brace [4]
Concentric brace
Buckling
restrained
brace
Yielding
brace
Buckling
brace
BRB yielding
in both
tension and
compression
BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

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Fig. 2. Hysteresis plot for buckling-restrained brace and
concentric brace [4]
BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

6. COMPOSITION
Unbonded
Material
Core
+
Casing
=
Concrete
Fig. 3. Composition of BRB [8]
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

7. DESIGN PROCEDURE
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

8. 6/21/2018 8
BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

9. FRAME LAYOUT AND CONFIGURATION
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Inverted V-bracing V-bracing Diagonal Bracing
(Same direction)
Diagonal Bracing (Zig-Zag) Multi-storey X-bracing
Fig. 5. BRBF Configurations [6]
BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

10. CASE STUDY
EXPERIMENTAL INVESTIGATION
BUCKLING RESTRAINED BRACED FRAMES

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Fig. 6. Frame Model With Loading Arrangement [3]
BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

12. APPLIED
LOAD (Kg)
STOREY
LEVEL
STOREY
DEFLECTION
(mm)
2.5
5
Top
Bottom
2.19
0.45
5
10
Top
Bottom
3.78
1.03
7.5
15
Top
Bottom
5.86
1.87
10
20
Top
Bottom
9.64
2.27
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Fig. 7 Load vs. Deflection for Un-Braced
Frame [3]
Table 1. Un-Braced Frame [3]
 DISCUSSION
BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

13. APPLIED
LOAD (Kg)
STOREY
LEVEL
STOREY
DEFLECTION
(mm)
2.5
5
Top
Bottom
0.96
0.34
5
10
Top
Bottom
2.4
0.99
7.5
15
Top
Bottom
3.31
1.22
10
20
Top
Bottom
6.66
2.81
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Fig. 8 Load vs. Deflection for
Conventionally Frame [3]
Table 2 Conventionally Braced Frame [3]
BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

14. 6/21/2018 14
APPLIED
LOAD (Kg)
STOREY
LEVEL
STOREY
DEFLECTION
(mm)
2.5
5
Top
Bottom
0.35
0.19
5
10
Top
Bottom
1.66
0.48
7.5
15
Top
Bottom
3.31
1.87
10
20
Top
Bottom
5.23
1.43
12.5
25
Top
Bottom
5.46
1.69
Table 3 Buckling Restrained Frame [3]
Fig. 9. Load vs. Deflection for
Buckling Restrained Braced Frame [3]
BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

15. • Lateral deflection of frame for a specific horizontal load is much less in
buckling restrained frame as compared to conventional braced frame, using
the same cross section of a brace.
• The average ratio of lateral displacement of conventional braced frame to
buckling restrained braced frame is 1.215. This shows BRB is more
effective in resisting the lateral deflection.
• The average ratio of lateral load caring capacity of conventional braced
frame to buckling restrained braced frame for a specified lateral deflection
is 1.33. This shows the lateral load caring capacity of BRB is more than
conventional brace.
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 RESULT
BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

16. ADVANTAGES
 Stable hysteretic behaviour and high energy dissipation
capacity
 It can be easily connected to the structural system
 Limited sensitivity to environmental condition changes
 It yields in both tension and compression
 The BRB element can if necessary be replaced after a
major seismic event.
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

17.  Depending on the configuration used, BRBF’s can give
lower foundation loads than comparable shear wall
systems
 It is easy to adopt in seismic retrofitting
 Does not usually require structural members and
foundation strengthening
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

18. DISADVANTAGES
 Lack of re-centering mechanism
 Lack of criteria for detecting and checking damaged
braces
 Ductility properties strongly affected by the geometry
and material type of the yielding steel core segment
 Further studies regarding the reliability of brace
connections to the frame are required
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

19. FUTURE DEVELOPMENTS
 Enhanced Seismic Stability and Residual Drift Control
Fig. 4. BRBF – SMRF [6] Fig. 5. BRBF - Elastic Truss
[6]
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

20.  Novel BRB Configurations
Fig. 6. Interior vertically oriented
BRBs at the base of frame [6]
Fig. 7. Exterior outrigger BRB [6]
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

21. APPLICATIONS
 Osaka International Convention Centre, Japan
 Casad Dam, US
 Wallace F. Bennet Federal Building, Utah
 One Rincon Hill Tower, San Francisco
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

22. CONCLUSION
 Behaves more effectively, when it is subjected to a
seismic force
 Provides the cost effective solution in lateral load
resisting system as compared to conventional brace
 BRB use the inherent ductility of steel to provide system
ductility
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Department of Civil Engineering

23. REFERENCES
 Bhargava Laxmi Goli et al. (2017), “ Analytical Study of Buckling Restrained
Frames Under Lateral Loads Using ETABS”, International Journal of Pure
and Applied Mechanics, 15, 431-435
 Gary S. Prinz & Paul W. Richards (2012), “Seismic Performance of Buckling-
Restrained Braced Frames with Eccentric Configurations”, American Society of
Civil Engineers, 138, 345-353
 Kumbhar Y D & Dr. Shiyekar M R (2014), “ Study of Buckling Restrained
Braces in Steel Frame Building”, International Journal of Engineering
Research and Applications, 4(8), 71-74
 Nayana Surendran & Asha Varma P (2017), “Buckling Restrained Braces
(BRB) – A Review”, International Research Journal of Engineering and
Technology, 4(3), 2320-2324
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

24.  Frames”, Modern Steel Construction
 Reza Bagerzadeh Karimi M et al. (2015), “Seismic Behavior of Steel Structure
with Buckling Restrained Braces”, International Journal of Civil and
Environmental Engineering, 9, 503-511
 Robinson K S (2014), “Advances in design requirements for Buckling
Restrained Braced frames”, New Zealand Society for Earthquake Engineering
Conference
 Ryan A. Kersting & Larry A. Fahnestock, Walterio A. López (2015), “Seismic
Design of Steel Buckling-Restrained Braced Frames”, National Institute of
Standards and Technology
 Yamini Komath & Preethi M (2017), “Review On Structural Performance Of
Braced Steel Sturtures Under Dynamic Loading”, International Research
Journal of Engineering and Technology, 4(6), 1535-1539
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BUCKLING RESTRAINED BRACED FRAMES
Department of Civil Engineering

25. Thank you