ENHANCEMENT OF SEISMIC PERFORMANCE OF

STRUCTURES USING HyFRC

by Needhi Kotoky

Under the supervision ofDr. Anjan Dutta and Dr. Sajal K. Deb

Department of Civil EngineeringIndian Institute of Technology Guwahati

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MOTIVATION

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Concrete is the most widely used constructionmaterial

Improve performance of earthquake resistantstructures are good ductility and higher energyabsorption capacity

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Brittleness of concrete can be overcome by theinclusion of randomly distributed fibres

USE OF FRC

Use of fibres in concrete removes weaknesses of

concrete-

low crack growth resistance

high shrinkage cracking

low durability, etc

The use of two or more types of fibres in suitable

combinations helps to arrest crack from micro to

macro level

Using mixes incorporating different types of fibre is

therefore advantageous

This process is referred as hybridization

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USE OF HyFRC

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Commonly used fibers for Hybrid Fibre ReinforcedConcrete (HyFRC) are-

Steel

Glass

Synthetic fibres like- Polypropylene, Polyester

Carbon fibre

For the present study, Steel fibre of two sizes and

Polypropylene fibre of two different brands available

in India are used

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Inclusion of steel fibres in the

concrete mix is an effective way of

reducing macro-cracking, whilst

polypropylene fibres are very good

at arresting micro-cracking

Enhance impact strength and

toughness

Better fibre proportion is judged

on the basis of toughness

Fibers bridging crack in a HyFRC tested beam

ADVANTAGE OF HyFRC

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Material characterization for HyFRC

Evaluation of best possible combinations based on

toughness of concrete considering prism

specimens

OBJECTIVE OF THE RESEARCH

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The research aims to provide an enhanced understandingon the use of HyFRC on the seismic performance of prismspecimen

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FibresAspect

ratio

Tensile strength

(MPa)Geometry

Steel fibre

(Dramix 65mm and

35mm)

65 1150Hooked

end

FIBRES USED IN TESTING

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FibresAspect

Ratio

Tensile strength

(MPa)Geometry

Polypropelene fibre I

(Recron 3s)

600 450 Triangular flat

Polypropelene fibre II

(Bajaj Plast)

550 670 Fibrillated

(Mesh)

FIBRES USED IN TESTING

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FIBRE PROPORTION

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Fibre

Mix

Steel

(%)

PP (%)

Type 1

PP (%)

Type 2

PL - - -

A1 0.8 0.15 -

A2 0.8 0.2 -

A3 1 0.15 -

A4 1 0.2 -

A5 1.2 0.15 -

A6 1.2 0.2

B1 0.8 - 0.15

B2 0.8 - 0.2

B3 1 - 0.15

B4 1 - 0.2

B5 1.2 - 0.15

B6 1.2 - 0.2NCCE-2017

MIXING PROCEDURE FOR DIFFERENT CONSTITUENTS

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COMPRESSIVE STRESS-STRAIN CURVE

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TENSILE STRESS- STRAIN CURVE

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ASTM C 1018

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TOUGHNESS EVALUATION

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Concerns with ASTM C 1018 and JSCE SF4 for toughnesscalculation–

Locating first crack point on the curve is highlysubjective and as such toughness indices measured byASTM C 1018 are highly operator dependent

JSCE produces toughness parameter that is too broadand hence unable to distinguish between compositeresponses at different crack openings

Technique proposed by Banthia and Trottier-

Post Crack Strength (PCS) method produces toughnessparameter that do not require the identification of firstcrack

Calculated from post peak energy

Pre-peak energy is omitted for calculation

Total energy also not requiredNCCE-2017

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POST CRACK STRENGTH METHOD (PCS)

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TEST SET UP

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150 x 150 x 700 mm beam specimen is tested underthree point loading according to ASTM C 1018 toevaluate toughness of the specimen by the PCSmethod.

HyFRC specimen showed better flexural strengththan conventional concrete specimen

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VeeBeeTime (sec)

Maximum load withstand by the specimen

(KN)

Modulus of rupture (Mpa)

15 29.8 6.2

RESULTS

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VeeBeeTime (sec)

Maximum load withstand by the specimen

(KN)

Modulus of rupture (Mpa)

2 18.4 3.8

Conventional concrete specimen

HyFRC specimen

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LOAD-DEFORMATION CURVE

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Conventional concrete fails suddenly once thedeflection corresponding to the ultimate flexuralstrength is exceeded

HyFRC continues to sustain considerable load evenwhen deflection is considerably in excess of thefracture deflection of the conventional concrete

HyFRCCONVENTIONAL CONCRETE

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TOUGHNESS EVALUATION OF THE PRISMS

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Specimen Type

Average compressive

strength (MPa)

Maximum load applied to the specimen (KN)

Toughness (MPa)

Modulus of rupture(MPa)

PL 34.23 18.27 0.34 3.9A1 34.96 24.8 2.47 5.8A2 33.65 27.44 2.67 5.7A3 35.31 28.16 2.97 6.7A4 34.22 20.18 2.11 4.9A5 33.44 25.82 2.54 5.6A6 34.6 25.07 2.57 5.7B1 34.04 19.54 1.91 4.8B2 34.65 17.98 1.87 5.1B3 33.98 20.73 2.22 5.8B4 34.17 22.32 2.45 4.3B5 33.34 23.41 2.53 5.1B6 34.16 25.1 2.61 5.2

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Fractures specimen of HyFRC shows that failure takesplace primarily due to fiber pull-out or debonding

Unlike conventional concrete, HyFRC specimen doesnot break immediately after initiation of first crack

This has the effect of increasing work of fracturereferred as toughness – represented by area under theload-deflection curve

Influence of fibres on concrete is reflected by flexuralstrength

Best proportion is found to be 1% steel and 0.15%polypropelene (Recron 3s) in term of toughness

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CONCLUDING REMARKS

Soleimani, S.S. (2002). Flexural response of hybrid fibercementitious composites. Master thesis, The university of BritishColumbia

Banthia, N., Trottier, J.F. (1995). Test methods for flexuraltoughness characterization of fiber reinforced concrete: someconcerns and a proposition. ACI Materials Journal, vol. 92, no. 1,pp. 48-57.

Bentur, A., & Mindess, S. (2006). Fibre reinforced cementitiouscomposites. CRC Press.

American Concrete Institute. (2002).State-of-the-Art Report onFiber Reinforced Concrete. ACI 544.1R-96

Banthia, N., Soleimani, S.M. (2005). Flexural response of hybridfiber reinforced cementitious composites, ACI Materials Journal,vol. 102, no. 5.

American Society for Testing and Materials. (1989). Standard TestMethod for Flexural Toughness and First-Crack Strength of FiberReinforced Concrete (Using Beam with Third Point Loading). ASTMStandards for Concrete and Aggregates, vol. 04.02, StandardDesignation C1018, pp. 499-505

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REFERENCES

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Qian, C.X., Stroeven, P. (2000). Development of hybridpolypropylene-steel fibre-reinforced concrete, Cement andConcrete Research, vol. 30 , pp. 63–69

Sivakumar,A., Manu Santhanam,M. (2007). Mechanical propertiesof high strength concrete reinforced with metallic and non-metallic fibres. Cement & Concrete Composites, vol. 29 , pp. 603–608

Ganesan,N., Indira,P.V., Sabeena,M.V. (2014). Behaviour of hybridfibre reinforced concrete beam–column joints under reverse cyclicloads. Materials and Design, vol. 54 ,pp. 686–693

Japan Concrete Institute. (1983). Method of Test for FlexuralStrength and Flexural Toughness of Fiber Reinforced Concrete.Standard SF4, JCI Standards for Test Methods of Fiber ReinforcedConcrete, pp. 45-51.

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REFERENCES

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