土木建筑毕业设计中英文翻译1.docx

土木建筑毕业设计中英文翻译1.docx

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土木建筑毕业设计中英文翻译1

外文资料

STUDIESONIMPACTSTRENGTHOFCONCRETESUBJECTEDTOSUSTAINED

ELEVATEDTEMPERATURE

SureshNARAYAN

Concretehasaremarkablefireresistingproperties.Damageinconcreteduetofiredependsonagreatextentontheintensityanddurationoffire.Spallingcrackingduringheatingarecommonconcretebehaviourobservedintheinvestigationofthefireaffectedstructures.Plentyofliteratureisavailableonthestudiesofconcretebasedontimetemperaturecures.Inpower,oilsectorsandnuclearreactorsconcreteisexposedtohightemperatureforconsiderableperiodoftime.Theseeffectscanbereckonedasexposuretosustainedelevatedtemperature.Thesustainedelevatedtemperaturemaybevaryingfromafewhourstoanumberofyearsdependinguponpracticalconditionofexposures.Theknowledgeonpropertiesundersuchconditionsisalsoofprimeimportanceapartfromthestructuressubjectedtohighintensityfire.Impactstudiesofstructuresubjectedtosustainedelevatedtemperaturebecomesmoreimportantasitinvolvessensitivestructureswhichismorepronetoattacksandaccidents.Inthispaperimpactstudiesonconcretesubjectedtosustainedelevatedtemperaturehasbeendiscussed.Experimentshavebeenconductedon180specimensalongwith180companioncubespecimens.Thetemperaturesof100°C,200°Cand300°Cforadurationofexposureof2hours4hoursand6hourshasbeenconsideredintheexperiments.Theresultsarelogicallyanalyzedandconcluded.

1.INTRODUCTION

Theremarkablepropertyofconcretetoresistthefirereducesthedamageinaconcretestructurewheneverthereisanaccidentalfire.Inmostofthecasestheconcreteremainsintactwithminordamagesonly.Thereasonbeinglowthermalconductivityofconcreteathighertemperaturesandhencelimitingthedepthofpenetrationoffiredamage.Butwhentheconcreteissubjectedtohightemperatureforlongdurationthedeteriorationofconcretetakesplace.Henceitisessentialtounderstandthestrengthanddeformationcharacteristicsofconcretesubjectedtotemperatureforlongduration.InthispaperanattempthasbeenmadetostudythevariationinImpactStrengthofconcretewhensubjectedtoatemperaturerange100oC,200oCand300oCsustainedforaperiodof2hrs,4hrsand6hrs.

Thereviewoftheliteratureshowsthatalotofresearchwork[1–3]hastakenplaceontheeffectofelevatedtemperatureonconcrete.Allthesestudiesarebasedontime–temperaturecurves.Henceanattempthasbeenmadetostudytheeffectofsustainedelevatedtemperatureonimpactstrengthofconcreteandtheresultsarecomparedwiththecompressivestrength.Theexperimentalprogrammehasbeenplannedforunstressedresidualstrengthtestbasedontheavailablefacilities.Residualstrengthisthestrengthofheatedandsubsequentlycooledconcretespecimensexpressedaspercentageofthestrengthofunheatedspecimens.

2.EXPERIMENTALINVESTIGATION

2.1.TESTSPECIMENANDMATERIALS

Atotalof180specimensweretestedinthepresentstudyalongwith180companioncubes.Anelectricovencapableofreachingamaximumtemperatureof300oChasbeenusedforinvestigation.FineandcoarseaggregatesconformingtoIS383hasbeenusedtopreparethespecimenwithmixproportionsM1=1:

2.1:

3.95w/c=0.58,M2=1:

1.15:

3.56w/c=0.53,M3=1:

0.8:

2.4w/c=0.4.

2.2TESTVARIABLES

Theeffectsofthefollowingvariableswerestudied.

2.2.1Sizes

SizeofImpactStrengthTestSpecimenwas150mmdialand64mmthicknessandsizeofcompanioncube150x150x150mm.

2.2.2MaximumTemperature

Inadditiontoroomtemperature,theeffectofthreedifferenttemperatures（100oC,200oCand300oC）onthecompressivestrengthwasinvestigated.

2.2.3ExposureTimeatMaximumTemperature

Threedifferentexposuretimeswereusedtoinvestigatetheinfluenceofheatoncompressivestrength;theyare2hrs,4hrsand6hrs.

2.2.4CoolingMethod

Specimenswerecooledinairtoroomtemperature.

3.TESTPROCEDURE

AllthespecimenswerecastinsteelmouldsasperIS516andeachlayerwascompacted.Specimenswerethenkeptintheirmouldsfor24hoursafterwhichtheyweredecoupledandplacedintoacuringtankuntil28days.Afterwhichthespecimenswereremovedandwereallowedtodryinroomtemperature.Thesespecimenswerekeptintheovenandtherequiredtargettemperaturewasset.Dependingonthenumberofspecimenkeptinsidetheoventhetimetakentoreachthesteadystatewasfoundtovary.Afterthesteadystatewasreachedthespecimensweresubjectedtopredeterminedsteadydurationattheendofwhichthespecimensarecooledtoroomtemperatureandtested.

ACIdropweightimpactstrengthtestwasadopted.Thisisthesimplestmethodforevaluatingimpactresistanceofconcrete.Thesizeofthespecimenis150mmdialand64mmthickness.Thediscspecimenswerepreparedusingsteelmouldscuredandheatedandcooledas.Thisconsistsofastandardmanuallyoperated4.54kghammerwith457mmdrop.A64mmhardenedsteelballandaflatbaseplatewithpositioningbracketandlugs.Thespecimenisplacedbetweenthefourguidespieces（lugs）located4.8mmawayfromthesample.Aframe（positioningbracket）isthenbuiltinordertotargetthesteelballatthecentreofconcretedisc.Thedisciscoatedatthebottomwithathinlayerofpetroleumjellyorheavygreasetoreducethefrictionbetweenthespecimenandbaseplate.Thebottompartofthehammerunitwasplacedwithitsbaseuponthesteelballandtheloadwasappliedbydroppingweightrepeatedly.Theloadingwascontinueduntilthediscfailedandopenedupsuchthatittouchedthreeofthefourpositioninglugs.Thenumberofblowsthatcausedthisconditionisrecordedasthefailurestrength.Thecompanioncubesweretestedforcubecompressionstrength（fake）.

4.ANALYSISANDRESULTS

4.1RESIDUALCOMPRESSIVESTRENGTHVS.TEMPERATURE

FromTable1,at100°CsustainedelevatedtemperatureitisseenthattheresidualstrengthofaircooledspecimensofmixesM1,M2andM3hasincreasedinstrength114%forM1mix,109%forM2mixand111%forM3mixfor6hoursdurationofexposure.Whenthesustainedelevatedtemperatureisto200°Cforaircooledspecimensthereisadecreaseinstrengthupto910%approximatelyforM1mixforadurationof6hours,butincaseofM2mixitis82%andforM3mixitis63%maximumfor6hoursdurationofexposure.WhentheconcretemixesM1,M2andM3areexposedto300°Csustainedtemperaturethereisareductioninstrengthupto78%forM1mixfor6hourdurationofexposure.

4.2RESIDUALCOMPRESSIVESTRENGTHVSDURATIONOFEXPOSURE

FromTable1,resultshowsthatheatingupto100°Cfor2hoursand4hours,theresidualstrengthofmixM1hasdecreasedwhereastheresidualstrengthofmixM2andM3hasincreased.Theresidualstrengthisfurtherincreasedfor6hoursdurationofexposureinallthethreemixesM1,M2andM3evenbeyondthestrengthatroomtemperature.WhenthespecimensofmixesM1,M2andM3areexposedto200°Cfor2,4and6hoursofduration,itisobservedthattheresidualstrengthhasdecreasedbelowtheroomtemperatureandhasreached92%forM1mix,82and73%forM2andM3mixrespectively.ConcretecubesofmixesM1,M2andM3whensubjectedto300°Ctemperaturefor2,4and6hourstheresidualstrengthformixM1reducesto92%for2hoursupto78%forsixhoursdurationofexposure,forM2mix90%for2hoursdurationofexposureupto76%forsixhourdurationofexposure,forM3mix88%upto68%between2and6hoursofdurationofexposure.

5.IMPACTSTRENGTHOFCONCRETE

5.1RESIDUALIMPACTSTRENGTHVSTEMPERATURE

Fromthetable1,itcanbeobservedthatforthesustainedelevatedtemperatureof100°Ctheresidualimpactstrengthofallthespecimensreducesandvarybetween20and50%formixM1,15to40%formixM2andM3.Whenthesustainedelevatedtemperatureis200°Ctheresidualimpactstrengthofallthemixesfurtherdecreases.Thereductionisaround60-70%formixM1,55to65%forM2andM3mix.Whenthesustainedelevatedtemperatureis300°Citisobservedthattheresidualimpactstrengthreducesfurtherandvarybetween85and70%formixM1and85to90%formixM2andmixM3.

5.2RESIDUALIMPACTSTRENGTHVSDURATIONOFEXPOSURE

FromtheTable1andFigures1to3,itcanbeobservedthatthereisareductioninimpactstrengthwhenthesustainedelevatedtemperatureis100°Cfor2hrs,4hrsand6hrs,anditsrangeis15to50%forallthemixesM1,M2andM3.TheinfluenceofdurationofexposureishigherformixM1whichdecreasesmorerapidlyascomparedtomixM2andmixM3forthesamedurationofexposure.Whenthespecimensaresubjectedtosustainedelevatedtemperatureof200°Cfor2,4and6hourofduration,furtherreductioninresidualimpactstrengthisobservedascomparedtoat100°C.Thereductionisintherangeof55-70%forallthemixes.Thesixhourdurationofexposurehasagreaterinfluenceontheresidualimpactstrengthofconcrete.Whenthesustainedelevatedtemperatureis300°Cfor2,4and6hoursdurationofexposuretheresidualimpactstrengthreduces.Itcanbeseenthatbothtemperatureanddurationofexposurehaveaveryhighinfluenceontheresidualimpactstrengthofconcretewhichshowsareductionupto90%approximatelyforallthemixes.

Table1.Residualimpactstrengthandresidualcompressivestrength

Temperature

Durationofexposue

Residualimpact

Strengthatfailure

ResidualcompressivestrengthinN/mm2

%variationinresidualimpactstrength

%variationinresidualcompressivestrengt

°C

Hours

I1

I2

I3

M1

M2

M3

ri1

ri2

ri3

M1

M2

M3

0

41.3

49

66

33

44

60

100

100

100

100

100

100

100°C

2

4

6

33.6

24

19.3

43

36

29

54

52