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INTERNATIONALJOURNALOFCIVILANDSTRUCTURALENGINEERING

Volume2,No4,2012

Copyright2010AllrightsreservedIntegratedPublishingservices

ResearcharticleISSN09764399

ReceivedonMarch,2012PublishedonMay20121138

Flexuralbehaviourofsteelfiberreinforcedhighstrengthricehuskash

cementconcretesimplysupportedbeamsVeeraReddy.M

Professor,CivilEngineeringDepartment,KakatiyaInstituteofTechnologyandScience,Warangal-506015(AP),India

[email protected]

doi:10.6088/ijcser.00202040012

ABSTRACT

The experimental programme was designed to study the flexural behaviour of simply

supportedbeamscastwithsteelfiberreinforcedhighstrengthricehuskashcementconcrete.

ThevariablesinthestudyareVolumeofsteelfibersandlongitudinalreinforcement.Twelve

rectangularreinforcedconcretebeamsarecastandtestedundertwo-pointloading.Moments

andcurvaturesarecalculatedfromtheexperimentaldataandtheMoment-curvaturediagramsarepresented inthispaper.Fromthe experimental data, it isobserved that the additionof

steelfibersmadetheRCsectionstobehaveinaductilemannerevenifthesectionsareover

reinforced.

Keywords:RiceHuskAsh,metalfibers,highstrengthconcrete,flexure,two-pointloading

1.Introduction

According to ACI code, concrete with compressive strength higher than 41Mpa may

classified ashigh strengthconcrete(ACIcommittee, 1984).Useofhigh strengthconcrete

resultsin reduceddeadloadsinlargespanandtallerstructures.Asthepost-peakportionofitsstress-straindiagramdescendsdeeplywithincreaseincompressivestrength,highstrength

concrete is considered as a relatively brittle material (ACI committee, 1975, 1993,Veera

Reddyetal.,2007).Usageofhighstrengthconcreteislimitedduetotheinverserelationship

betweenstrengthandductility.Acompromisebetweenstrengthandductilitycanbeobtained

by using discontinuous fibers. However very littlework has been done to investigate the

possibilityofusingsteelfibersinenhancingflexuralductilityofhighstrengthricehuskash

cementconcretebeams.Thecurrentexperimentalstudyconsistsofcastingtwelverectangular

reinforcedconcretebeamsandtestingundertwo-pointloading.Thetwelvebeamsconsistsof

sixunderreinforcedandsixoverreinforcedbeams.Thesteelfibercontentwasaddedinboth

underandoverreinforcedbeamsviz.,0%,0.3%,0.6%,0.9%,1.20%and1.50%.

2.ExperimentalProgramme

In this study, Themix design for concretewas doneusing graphicalmethod proposedby

Erntroy and Shacklock as reported by Krishna Raju ( Krishnaraju, 2012). The final mix

proportionsare1:1.00:1.91:0.26(cement:sand:coarseaggregate:water-binderratio)with

acementcontentof580kg/m3ofconcrete,5%ofcementwasreplacedwithRHA.

Table1givesthedetailsoftestedsimplysupportedreinforcedbeamscastwithabovemix

proportions ( Designed as per IS codes). After 28 days curing period the beams were

whitewashed.Thenwithhelpofpencilandscale,thelocationofsupports,loadpoints,the

positionswherecurvaturemeterframesandthedeflectiongaugehavetobeplacedduringthetest,weremarkedonbeamsandkeptreadyforthetesting.Allthebeamsweretestedunder


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Flexuralbehaviourofsteelfiberreinforcedhighstrengthricehuskashcementconcretesimplysupported

beams

VeeraReddy.M

InternationalJournalofCivilandStructuralEngineering

Volume2Issue42012

1139

symmetricaltwopointsloadingonasimplysupportedspan900mm.Figure1showsthetest

set-upofsimplysupportedbeams.Strainratecontrolwasusedtoobtainthecompleteprofile

ofmoment-curvaturebehaviour,especiallyinthepostultimateregion.Speciallyfabricated

curvaturemeterswereusedtomeasurethecurvaturesinthecentral150mmofthebeam.The

curvaturemeterconsistsoftworectangularframesmadeoutofa12mmsquaremildsteelbar.Eachframecanfixtothebeambymeansoftwoscrewsof6mmdiameterontheeithersides

of the beamleaving equaldistances on the each side.Two dial gauges of0.002mm least

count and 12mm travel were fixed between two rectangular frames, one at the top and

anotheratthebottom.Thedeformationsindicatedbydialgaugesdividedthegaugelength

givesthestrainsatthatlevelarerecordedcorrespondingtoeachload.Fromtheexperimental

datathemomentsandcurvaturesarecalculatedforallSteelfiberreinforcedhighstrengthrice

huskashcementconcretebeams(LokandXiao,1999andSabgapathi.PandAchuta,1989).

3.ResultsandDiscussions

The specimen calculations for moments and curvatures are presented in Table 2. Themoment-curvaturediagramsaredrawnforallthebeams.Themomentcurvaturediagramsfor

ORBeamsareshowninfigure2.ThemomentcurvaturediagramsforURBeamsareshown

infigure3.Theunderandover reinforcedbeamsofarefailedinductilemanner,which is

achievedbyaddingsteelfibers.Thefailurepatternsofunderandoverreinforcedbeamsare

showninfigure4.

Table1:DetailsofExperimentalProgramme.

Reinforcementdetails Stirrupsteel FiberdetailsSl

No B

ea

m

Design

ation

DiaNo

Barsfy Dia

Spa

cingfy Dia

Vol.

(%)fy

f'c

1 URB1 8 2 430 8 80 430 0.55 0.00 315 48.65

2 URB2 8 2 430 8 80 430 0.55 0.30 315 57.65

3 URB3 8 2 430 8 80 430 0.55 0.60 315 58.55

4 URB4 8 2 430 8 80 430 0.55 0.90 315 60.80

5 URB5 8 2 430 8 80 430 0.55 1.20 315 61.42

6 URB5 8 2 430 8 80 430 0.55 1.50 315 63.80

7 ORB110

20

2

2

425

435 8 80 430 0.55 0.00 315 48.65

8 ORB210

20

2

2

425

4358 80 430 0.55 0.30 315 57.65

9 ORB310

20

2

2

425

4358 80 430 0.55 0.60 315 58.55

10 ORB410

20

2

2

425

4358 80 430 0.55 0.90 315 60.80

11 ORB510

20

2

2

425

4358 80 430 0.55 1.20 315

61.42

12 ORB6 102022

425435

8 80 430 0.55 1.50 315 63.80


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Table2:SampleobservationsandcalculationsforsimplysupportedbeamORB6

Curvature

Readings

Curvature

ReadingsSl.

No

Load

(kN)Top Bottom

CurvatureMoment

(kN-m)Sl.

No

Load

(kN)Top Bottom

CurvatureMoment

(kN-m)

1 0 0 0 0.00E+00 0 23 92.12 85 85 2.13E-05 17.273

2 3.92 0 0 0.00E+00 0.735 25 95.06 89 90 2.24E-05 17.824

3 7.84 1 0 1.25E-07 1.47 26 99.96 90 92 2.28E-05 18.743

4 11.76 6 0 7.50E-07 2.205 27 107.8 93 95 2.35E-05 20.213

5 17.64 13 0 1.63E-06 3.308 28 113.7 103 100 2.54E-05 21.315

6 21.56 15 1 2.00E-06 4.043 29 115.6 106 105 2.64E-05 21.683

7 25.48 20 4 3.00E-06 4.778 30 117.6 112 110 2.78E-05 22.05

8 29.4 22 6 3.50E-06 5.513 31 122.5 117 115 2.90E-05 22.969

9 33.32 25 9 4.25E-06 6.248 32 126.4 120 120 3.00E-05 23.704

10 38.22 30 13 5.38E-06 7.1663 33 131.3 125 130 3.19E-05 24.623

11 42.14 33 20 6.63E-06 7.9013 34 135.2 130 135 3.31E-05 25.358

12 46.06 38 25 7.88E-06 8.6363 35 141.1 145 150 3.69E-05 26.460

13 49.98 43 30 9.13E-06 9.3713 36 143.1 155 160 3.94E-05 26.828

14 53.9 46 35 1.01E-05 10.106 37 146 205 175 4.75E-05 27.379

15 57.82 50 40 1.13E-05 10.841 38 149.9 235 210 5.56E-05 28.114

16 61.74 56 44 1.25E-05 11.576 39 152.9 335 275 7.63E-05 28.665

17 63.7 60 50 1.38E-05 11.944 40 149 535 320 1.07E-04 27.930

18 69.58 63 54 1.46E-05 13.046 41 141.1 635 1090 2.16E-04 26.460

19 74.48 67 58 1.56E-05 13.965 42 132.3 1830 1200 3.79E-04 24.806

20 79.38 72 62 1.68E-05 14.8838

21 83.3 75 70 1.81E-05 15.619

22 87.22 80 80 2.00E-05 16.359

Figure1:Testset-upofsimplysupportedbeams


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Figure2:Themoment-CurvaturediagramsforORBeams

Figure3:ThemomentCurvaturediagramsforURBeams

Figure4:ThefailurepatternofURandORbeams


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4.Conclusions

Thefollowingconclusionsaredrawnfromtheexperimentalstudy

1.Theadditionofsteelfibersandricehuskashtohighstrengthconcreteimprovedmomentandcurvature.

2. The improvementofcurvature is12% to94% inunder reinforced beamsand 11% to197%inoverreinforcedbeams,duetoadditionofsteelfibersin0.3%to1.50%volume

ofconcrete.

3. Theimprovementofmomentis6%to35%inunderreinforcedbeamsand5%to36%inover reinforced beams, due to addition of steel fibers in 0.3% to 1.50% volume of

concrete.

4. TheadditionofsteelfibersmadetheRCsectionstobehaveinaductilemannerevenifthesectionsareoverreinforced.

5.References

1. ACICommittee363.,(1984),State-of-the-artreportofhighstrengthconcrete.(ACI363-R84),ACIJournal,81(4),pp364-411.

2. ACICommittee318.,(1995),Buildingcoderequirementsforstructuralconcrete(ACI319-95)andcommentary,ACI,FarmingtonHills,Michigan,pp369

3. ACICommittee544.,(1973),StateoftheartReportonFiberReinforcedConcrete,ACIJournal,70,pp724-744.

4. IS:12269-(1987),Specificationfor53GradeordinaryPortlandcement.5. IS:383-(1970),SpecificationforCoarseandFineAggregatesfromnaturalsources

forconcrete(Secondrevision).

6. IS:456 (2000),Plain andreinforced concrete-Codeofpractice, Bureauof IndianStandards,NewDelhi.

7. IS: 10262 (1982), Recommended guidelines for concrete mixdesign, Bureau ofIndianStandards,NewDelhi.

8. IS: 9399 (1979),Specification for apparatus for flexural testingofconcrete. BISNewDelhi

9. KrishnaRaju.N.,(2012),DesignofConcreteMixes,CBSPublishersandDistributors,Delhi.

10.Lok,T.S.andXiao,J.R.,(1999),Flexuralstrengthassessmentofsteelfiberreinforcedconcrete,JournalofMaterialsinCivilEngineering.11(3),pp188-196.


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11.ManishVarma,UmeshPendharkar,RaviK.Sharma,(2012),Experimentalstudytoevaluateshort-termdeflectionsfortwo-wayRCslabs,InternationalJournalofCivil

andStructuralEngineering,2(3),pp901-913.

12.Nehdi.M,DamattyA.E,Rahimi,R, (2003),Investigationon lap-joint behaviour ofGFRPplatesbondedtoSilicafumeandRicehuskashconcrete,InternationalJournal

ofAdhesionandAdhesives,23(4),pp323333.

13.Sabapathi, P. and Achuta, H., (1989), Analysis of steel fiber reinforced concretebeamsIndianConcreteJournal,pp246252.

14.Shende.A.M.Pande.A.M.(2011),ComparativestudyonSteelFibreReinforcedcumControl Concrete under flexural and deflection, International Journal of Civil and

StructuralEngineering,1(4),pp942-950.

15.Veera Reddy. M and Seshagiri Rao. M.V., (2007), A Mathematical Stress-StrainModelforHigh-StrengthSteel-FiberReinforcedConcreteUnderAxialCompression,

InternationalJournalofScientificComputing,2,pp7-18.

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