Buckling Restrained Braces

BY ▸ R.SIVA NAGARAJU▸ L .TRINATH

Contents

▸ Introduction▸ Types of braces▸ Why use BRBF▸ Components▸ Characteristics▸ Connections▸ Tests ▸ Survey ▸ Advantages▸ Reference structures▸ Conclusion

Introduction • The concept of Buckling

Restrained Braces developed in Japan by NIPPONS STEEL in 1980’s.

• It is designed to allow 1. Cyclic lateral loads on building 2. Earth quake induced loads

• 1. Specially Concentrically Braced (Frame)

• 2. Buckling Restrained Braced (Frame)

TYPES OF BRACES

Specially Concentrically Braced frame

Buckling Restrained Braced frame

Why we use BRBF?

• This structure has high stiffness & high ductility.

• It yields in both compression and tension• (no buckling).• It is a safe guard for building under

lateral loadings coming from earthquake forces.

• This can be moulded by using parameters like storey drift & base shear.

COMPONENTS

• 1. Steel core

• 2. Casing

• 3. Debounding material

Buckling- Restrained Brace:Steel Core+Casing

AA

Section A-A

Steel Core

Debonding material

Casing

Steel jacketMortar

Buckling Restrained Brace

Characteristics

• It prevents the members from buckling.

• It illustrates the envelope of hysteresis curve.

• It acts as a back bone of curve.

Connections

• 1. Welded

• 2. Pinned

• 3. Bolted

Welded connections

Pinned connections

Bolted connections

Literature surveyS. No Title Author Name Journal Published objective

1. Behavior and design of structures with buckling-restrained braces

Kim, J., et al. ELSEVIERVol:26 (2004)

Maximun displacements, story drifts, story shears.

2. Design of buckling-restrained braced frames using nonlinear time history analysis and optimization

Richard, J. B., et al.

ASCEVol: 135 (2009)

Nonlinear time history analysis and optimiztion compared to equivalent lateral forces.

3. Application of buckling-restrained braces in prefabricated reinforced concrete frame

Hongnan, w., et al.

Scientific.netVol: 351 (2013)

Retrofit of BRB to the old prefabricated building.

4. Performance of BRBF and Comparing it with the OCBF

Talebi, E., et al. International Journal of Civil

Design of BRBFs compared with OCBFs under earthquake loads.

TESTS

1. Brace test

2. Sub-assemblage test

Brace test specimen

Uniaxial Loading

Subassemblage test specimen Axial + Rotational Loading

Scale Requirements for Test Specimens

Brace Test Specimen

0.5 [ Pysc ]prototype [ Pysc ]specimen 1.5 [ Pysc ]prototype Subassemblage Test Specimen

[ Pysc ]specimen [ Pysc ]prototype

Advantages

• It is easy to erect.• Mostly used in seismic retro-

fittings.• It is an alternative for Specially

Concentrically Braced Frame.• When compared to SCBF, BRBF is

economical.

 University of California dormitory, Berkeley

seismic retrofitting

Fujita Corporation Headquarter: Tokyo

The new five-level, parking structure at John Wayne Airport (SNA) in Tustin

Rio Tinto Stadium,sandy

It minimises the Earth Quake intensity On the structure.

Using BRBF, will be a great step adopted by the Civil Enginners during Earthquake.

Conclusion

THANKS!

Any questions?