International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017
p-ISSN: 2395-0072
www.irjet.net
Buckling Restrained Braces (BRB) – A Review Nayana Surendran1, Asha Varma P2 PG Student, Department of Civil Engineering, NSS College of Engineering, Palakkad, Kerala, India 2 Professor, Dept. of civil Engineering, NSS College of Engineering, Palakkad, Kerala, India
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Abstract - Civil engineering structures are subjected to
such earthquake resisting system which is much more efficient than conventional concentric braces.
enormous cyclic forces during a seismic event. 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 type 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.
2. BUCKLING RESTRAINED BRACES(BRB) Buckling-Restrained Braces (BRBs) are a relatively recent development in the field of lateral load resisting structures. The early invention on BRB started in 80’s and its testing took place in mid-80’s. during 90’s it was implemented in Japan and because of its good response, this technology was transferred in US in 1998 whose testing and simulation took place in 1999 and then safely implemented in important projects after 2000. In 2000, the first BRB system is applied in North America as a primary lateral resisting system at UC Davis. The figure 1 shows the various stages in the development of BRB. The concept of BRB was first conceptualized by Wakabayashi a Japanese engineer. The first buckling-restrained brace that was made up of flat steel plate sandwiched between reinforced concrete panels.
Key Words: stable energy dissipation, concentrically-braced frames, Buckling Restrained Braces(BRB), inter story drifts, hysteresis loop
1.INTRODUCTION Earthquakes causes economic losses as well as losses of lives due to collapse of structures. During a severe earthquake event the main structural elements like beams and columns are seriously affected. When a building is subjected to seismic wave, large amount of energy is distributed within in the building and the level of damage sustained by the building depends on the dissipation of this energy. So a structural engineer has great concern in designing earthquake resisting system to dissipative energy effectively from the structure. The primary function of an energy dissipation element is to reduce the damage in main structural components. Bracings are widely used to stabilize the structure against the lateral loads generated due to wind, earthquakes etc. Main drawback of conventional bracing is the degradation of brace strength under compression due to buckling of the brace. BRB is an effective solution for this problem. Buckling restrained braced frame system is one
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Fig -1: Timeline of BRB system development The main component of BRBs consists of a steel core, which is encased by concrete which is shown in figure 2. The space between the tube and brace is filled with a concrete-like material and a special coating is applied to the brace to prevent it from bonding to the concrete. So that, the brace can slide with respect to the concrete-filled tube. The
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