Buckling restrained braced frames

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 21-Jun-18 2 BUCKLING RESTRAINED BRACED FRAMES Department of Civil Engineering

3. 21-Jun-18 3 BUCKLING RESTRAINED BRACED FRAMES Department of Civil Engineering NEED FOR A BETTER BRACE

4. FUNDAMENTALS OF BRB BEHAVIOUR 21-Jun-18 4 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

5. 21-Jun-18 5 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] 21-Jun-18 6 BUCKLING RESTRAINED BRACED FRAMES Department of Civil Engineering

7. DESIGN PROCEDURE 21-Jun-18 7 BUCKLING RESTRAINED BRACED FRAMES Department of Civil Engineering

8. 21-Jun-18 8 BUCKLING RESTRAINED BRACED FRAMES Department of Civil Engineering

9. FRAME LAYOUT AND CONFIGURATION 21-Jun-18 9 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

11. 21-Jun-18 11 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 21-Jun-18 12 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 21-Jun-18 13 Fig. 8 Load vs. Deflection for Conventionally Frame [3] Table 2 Conventionally Braced Frame [3] BUCKLING RESTRAINED BRACED FRAMES Department of Civil Engineering

14. 21-Jun-18 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. 21-Jun-18 15 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. 21-Jun-18 16 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 21-Jun-18 17 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 21-Jun-18 18 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] 21-Jun-18 19 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] 21-Jun-18 20 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 21-Jun-18 21 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 21-Jun-18 22 BUCKLING RESTRAINED BRACED FRAMES 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 21-Jun-18 23 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 21-Jun-18 24 BUCKLING RESTRAINED BRACED FRAMES Department of Civil Engineering

25. Thank you