Sura Presentation

8/10/2019 Sura Presentation

1/36

Fabrication and experimental investigation

of Buckling Restrained braced frame

under

Summer Undergraduate Research Awards(SURA)

Indian Institute of Technology,Delhi

Submitted by :

Amit Kumar Harsh Yadav

2011CE10327 2011CE10352

Facilitated By:

Prof D.R.Sahoo


2/36


3/36

Conventional CBFs (Concentrically

Braced Frames)

CBFs used to impart additional

strength to structural members

against earthquake loadings

Provide acceptable life safety

and collapse

preventionperformance

Tend to take load until breakage

or buckling

Brace: Provides extra stiffness to

the frame


4/36

DRAWBACKS

Normally very rigid and not very ductile

Member in compression prone to buckling

Permanent damage to structural members

Considerable residual drift

Significant economic impacts

unsymmetrical behavior in tension and compression

significant strength deterioration when loaded in

compression or on cyclic loading in inelastic range


5/36

What is BRBF??

The steel bars/plates are inserted in hollow steel section profilesfilled with concrete which provides restraining effect against lateralbuckling.

Source: Nippon Steel and Sumitomo Metal


6/36

Why use BRBF??

Resistant to buckling, so it can take compressive load

No permanent damage to structural members

Reduction in building repair requirements following an earthquake

source-Q. Xie / Journal of Constructional Steel Research 61 (2005) 727748

Unsymmetric behavior of

CBF on tension and

compresion

Symmetric hystereticdiagram in BRBFs


7/36

Work done in SURA

1-Design and fabrication of BRB

2-Material Testing

3-Testing of BRB

4-Test Results


8/36

Design and fabrication of BRB

Brace First, we designed the structural elements of BRBF like core brace, stiffness

members, steel hollow sections, end plates in AutoCAD.


9/36

Core Brace

End Plate


10/36


11/36

Buckling Restraining unit


12/36

Design of wooden braces to be used during casting of

concrete.

Casting of concrete in each half of steel hollow section with

wooden brace.

Removal of wooden brace from the hardened concrete.


13/36


14/36


15/36

Debonding material

Typically, a debonding material like

epoxy resin, silicon resin, vinyl tapes,etc. is used

We applied grease on the brace, kept itin the groove of buckling-restrainingpart as debonding material .

The ends of braces were bolted togusset plates as shown in next pictureand then the two ends of steel encasingsections were bolted to get bucklingrestrained brace


16/36

Bolting of two ends of steel casing with core brace.


17/36

Material Testing of mild steel used

During curing and hardening of concrete, we designed and

fabricate three steel coupons from the steel plates which

were used in our BRBF according to the provisions of

IS1608.

Then we performed uniaxial tensile testing on them in

Applied Mechanics lab to find its properties like yieldstrength, youngs modulus, etc.


18/36


19/36


20/36

-100

0

100

200

300

400

500

600

-0.05 0 0.05 0.1 0.15 0.2 0.25 0.3

Strain (mm)

Stress (MPa)

Coupon 1


21/36

-100

0

100

200

300

400

500

600

-0.05 0 0.05 0.1 0.15 0.2 0.25 0.3

Stress (MPa)

Strain (mm)

Coupon 2


22/36

-100

0

100

200

300

400

500

600

-0.05 0 0.05 0.1 0.15 0.2 0.25 0.3

Stress (MPa)

Strain (mm)

Coupon 3


23/36

Testing of BRB

The Standard Loading Protocol developed for this testing program was a

combination of the FEMA 450 loading sequences and OSHPD (Office

of Statewide Health Planning and Development) which is given below

1. 6 cycles of loading at the deformation corresponding to b=1.0by

2. 4 cycles of loading at the deformation corresponding to b=0.5bm

3. 4 cycles of loading at the deformation corresponding to b=1bm


5. 1 cycle of loading at the deformation corresponding to b=1.0bm





24/36

Standard Loading Protocol

source-Merritt, S., Uang, C.M. and Benzoni, G., Subassemblage testing of CoreBracebuckling-restrained braces. ReportNo. TR-2003/01, University of California, SanDiego, La Jolla, CA, 2003. page 20

Standard loading protocol


25/36

After this a low cycle fatigue loading protocol was imposed to the

test specimens, containing 30 cycles of loading at deformation

corresponding to b=1.5by

source-Merritt, S., Uang, C.M. and Benzoni, G., Subassemblage testing of CoreBracebuckling-restrained braces. Report

No. TR-2003/01, University of California, SanDiego, La Jolla, CA, 2003. page 21

Low Cycle Fatigue Protocol


26/36

Loading Protocol

loading protocol


27/36

Test Results

Stiffness

Brace -1

calculated by the slope of force vsdeformation curve shown below

The value of stiffness calculated is

25714.44 N/mm


28/36


29/36

Brace force vs deformation hysteretic curveBrace -1


30/36

Brace -2


31/36

Energy dissipated vs driftBrace-1


32/36

Brace-2


33/36

Conclusion

Plots for applied load versus brace deformation showed stable, balanced

hysteretic curve characteristic of full length buckling restrained brace .

Both test specimen performed well under the Standard Loading

Protocol and no fracture were observed. However the second test

specimen showed some slipping.

Since reduced length BRB exhibits similar brace force versus brace

deformation hysteretic curve and energy dissipating capacity as a full

length buckling restrained brace, we can safely conclude that a BRBcan be used as supplemental hysteretic dampers rather than primary

lateral force resisting members. Hence a reduced length BRB can be

used in combination with a conventional brace as a composite brace.


34/36

Future scope of work

The future scope of work in the project can be testing of acomposite brace made with combination of a reduced length

BRB and a conventional brace and comparison of result with

a full length buckling restrained brace to ascertain the

applicability of a composite brace

R f


35/36

References:

1. R. Tremblay, P. Bolduc, R. Neville and R. DeVall, Seismic testing and performan

buckling-restrained bracing systems Canadian Journal of civil engineering,2006.

2. Merritt, S., Uang, C.M. and Benzoni, G., Subassemblage testing of CoreBracebu

restrained braces. Report No. TR-2003/01, University of California, SanDiego, La 2003.

3. Qiang Xie, State of the art of buckling-restrained braces in Asia, Elsevier, 2004

4. James Newell, Chia-minh Uang, Gianmariao Benzoni, Subassemblage testing of

buckling-restrained braces (G Series).Repot No. TR-2006/01, University of CaliforLa Jolla, CA, 2003.

5. IS1608: Metallic Materials- Tensile Testing at ambient temperature 6. Rafael Sabelli and Walterio Lopez, Design of Buckling-Restrained Braced Frame

7. Federal Emergency Management Agency, NEHRP Recommended Provisions forSeRegulations for New Buildings and Other Structures, FEMA 450, Washington, D.C.,


36/36

THANK YOU

Sura Presentation

Documents

Transcript of Sura Presentation