毕设设计翻译.docx

毕设设计翻译.docx

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毕设设计翻译

Concretestressexperiment

1Introduction

Inthispaper，thestress—strainbehaviorofSFRCunderuniaxialtensionWasanalyzedfordifferenttypesoffiber．ThetensilecharacteristicsofSFRCinfluencedbythematrixstrengthandthesteelfibercontentwerestudiedalso．Inaddition，thestress—straincurvesofhighstrengthSFRCwithdifferentfactorswerewellacquired．Themechanismoffiberreinforcedconcretetoenhanceresearch,toobtainsteelfiberreinforcedconcreteintensioncurveofthewholeprocess,usingthemostappropriatemethodofaxialtension,buttomakesurethetestingmethodsimproved,andthetestingmachinemusthaveenoughstiffnesstoensurethetestingprocessstability.Iswellknowninengineeringpractice,process,technologyandeconomicconditionsduetoconstructionconstraints,SFRC-dopedfibervolumeintherateofgenerallynotmorethan2%,whilemostoftheengineeringexample,thefiberfractionareabout1%.InthispaperthedesignoftheaxialtensionSFRCmaterialtesting,fiberdosagetotake1%,andusingdifferenttypesoffiber-reinforcedforms,wereanalyzed.

2ExperimentalContent

Thespecimensweretestedona60kNuniversaltestingmachine．Fourhighsteelbarswereaddedtoenhancethestiffnessofthetestingmachine．Inaddition，spherichingeswereusedtoabatetheinitialaxialeccentricityofthespecimens．．

Itwasensuredthatspecimensshouldbepulledunderuniaxialtensionbyadjustingthefourhighstrengthboltswhichconnectthespecimenstothecrossbeam．Andthedifferencebetweenthetensilestrainsoftheoppositesidesofthespecimenshouldbelessthan15％oftheirmeanvalue．Whenthefibercontentwaslow（0and0.5％byvolume），thecyclicquirethewholestress—strain.

2．1Materials

FourtypesofsteelfibersshowninTablewerechosenforthistest．Threeofthesefibers（F1，F2andF3）werehooked—endandtheotherone（F4）wassmooth．

Threeconcretemixtures，showninTable2，wereinvestigated．WaterreducingagentswereusedinC60andC80mixes（DK一5madebyDalianStructureResearchInstituteandSikamadeinSwitzerlandrespectively）.ThecompressivestrengthsoftheseC30，C60，C80mixesweredeterminedaccordingto“TestMethodsUsedforSteelFiberReinforcedConcrete”（CECS13：

89）"83at28daysusing150mm×150mm×150mmcubes．Averagedresultsfor3specimensaregiveninTable2．0rdinaryPortlandcement（yieldedbyDalianHuanengOnodaCementCompany）of32．5and52．5（accordingtoChinastandard）werechosen．Riversand（modulusoffinenessis2.6）andcrushedlimestonecoarseaggregates（5—20Bin）wereused．

Table

Matrix

code

Strengthgrade

Ofcement

（ISO）

Cement

Kg/m3

u/c

ratio

Sand

ratio

Sand

Kg/m3

Crushed

Strne

Kg/m3

Water

reducing

Compressive

Strength

Mpa

C30

32.5

450

0.44

0.36

667

1155

----

37.07

C60

52.5

500

0.35

0.33

602

1223

DK-5

67.59

C80

52.5

600

0.29

0.31

535

1190

Sika

82.96

2．2Specimen

Thetensilespecimenwasbondedtosteelpaddingplatesatbothendsbytygoweld．Atotalof110specimensweredividedinto22groupsaccordingtocertainparameters．TheparametersofthesespecimensareshowninTable3．

2．3Items

Attheageof28days．plainconcreteandsteelfiberconcretespecimensweretestedfortensilestrength，respectively.Thetensilestress—straincurveswereacquired．Manyothertensilecharactersofthehighstrengthsteelfiberconcretesuchastensilework，etcwerecalculatedalso.Enhancedclasssteelfiberreinforcedconcretetoughnesscategorythanthestrengthofsteelfiberreinforcedconcreteanaverageof13%;whilecrackingfromthebasictothecrackwidthof0.5mminterval（thecorrespondingstrainofabout2000με）showedthefractureenergyintegral:

tougheningclasssteelfiberreinforcedconcreteenhancedclassthanthefractureenergyofsteelfiberreinforcedconcreteanaverageof20%.fromTable3alsoshowsthatmostoftheSFRCfirstpeakcorrespondstothelimitoftensilestrainvalueandplainconcreterather,inthe100μεaround,indicatingalowrateoffiber-containingincorporationinimprovingtheroleofultimatetensilestrainofconcreteisnotveryobvious.ThetougheningclassSFRCsecondpeakcorrespondstoamuchgreaterstrain,upto1000με,Fromthissecondpeakhasgreatlyenhancedtheappearanceoftoughness.DRAMIXFiberbecauseofthelengthofotherthreekindsoffiberlengthof2timesthefracturetoughnessandbetterinthetestcurvecanbeseeninthestrainisattained,theloadcontinuestomaintainahighlevelofintensity,untilthestrainwhentheloadsoastomaintain10000μεitspeaklevelof50%.

3ResultsandDiscussion

3．1Crackstressandultimatetensilestrength

ThecrackstressandultimatetensilestrengthofdifferentspecimensarelistedinTable3．Theadditionofsteelfibersintoconcreteincreaseditscrackstressandultimatetensilestrength．AndtheratiosofthesetwoparametersofSFRCtothoseofplainconcreue（withthesamemixproportion）aregiveninTable3，too．

3．1．1Effectofmatrixstrengthan（1fibertype

Fromtable3．Itcanbeseenthattheeffectsofsteelfibers0ncrackstressarelittleinfluencedbythematsixstrength．Thatistosay．Whenthematrixstrengthincreases,theratiosofcrackstressesofSFRC（withthesametypeoffiberscontained）tothoseofplainconcreteoneswiththesamemixproportionareinvariable．

However，theconditionforultimatetensilestrengthisdifferent．Whenthematrixstrengthincreases．theseratiosofultimatetensilestrengths（showninTable3）varydissimilarlyaccordingtothetypeofsteelfiber．Moreover．theincrementsarebiggerthanthoseofcrackstress．

TheheighteningefficiencyoffiberF1forultimatetensilestrengthrisesasmatrixstrengthincreases．Itisbecausethatthestrengthofthiskindoffiberisveryhigh（>1100MPa）．Nofiberbrokenwasobservedduringthetestandthehooked—endsofthefiberswerestraightenedwhenthematrixstrengthwashigh（C80）．Thehigherthematrixstrength．thiskindofsteelfibertakesonitsstrengtheningeffectmoreefficientlyfortheincreasingofbondstress．ThestrengthsoffibersF2andF3aremid—high（>700MPa）．Theyallhavehookedendsandbothoftheirsurfacesarecoarse．Whenthematrixstrengthwashigh（C80）．fiberbreakingoccurredinthetest．Andthisphenomenonimpairedtheheighteningefficiencyofthesetwokindsofsteelfiber．Sotheyshouldbeusedinmiddlestrengthconcretetoexerttheirstrengtheningeffectmoreefficiently．FiberF4issmooth．anditsbondstresswithmatrixiscomparativelylow．T}1erefore．itsstrengtheningeffectis1essnotablethanthoseofotherkindsoffiber．Becauseofthelowbondstress．nofiberbrokenwasfoundduringthetestanditsheighteningefficiencyforultimatetensilestrengthrisesasmatrixstrengthincreases．

3．1．2Effectoffibercontent

Theeffectoffibercontentonthecrackstressandu1．ultimatetensilestrengthwasinvestigatedforSFRCcontainedfiberF3．Andthefibercontentvariedfrom0．5％to1．5％byvolume（showninTable3）．ItcanbeseenfromFig．1andFig．2thatasthefibercontentincreases．

ThecrackstressandultimatestrengthofSFRCimproveobviously．Moreover．therisingtrendsofthecurvesinthesetwofiguresarestupendouslysimilar．Inotherwords，theeffectoffibercontentonthecharactersoftensilestressofSFRCispositiveandconsistent．

Table4Fibertypefactors

Fibercodeat

F10.642

F20.862

F30.794

F40.589

ThetensilestrengthofSFRCcanbecalculatedwiththefollowformula：

（1）

where，fftistheultimatetensilestrengthofSFRC；theultimatetensilestrengthofplainconcretewiththesamemixingproportion；a，thefibertypefactor，

whichisshownTable4；

isthefibercontent0fvolumeandl/distheaspectratioofsteelfibers.

3．2Tensilestrainandtoughnesscharacters

3．2．1Crackstrainandthestrainatpeaktensileload

Thetensilestrainswereacquiredbyaveragingthereadingsofthefourdisplacementsensorsfixedaroundthespecimen．Inaddition，thespecimenswhosedifferencebetweenthetensilestrainsofitsoppositesidesislargerthan15％oftheirmeanvaluewereblankedout．

ThecrackstrainorthestrainsatpeaktensileloadofSFRCaremuchbiggerthanthoseofplainconcrete（asshowninTable5）．Andtheincrementsgoupasthematrixstrengthorthefibercontentincreases．Comparedtothatoncrackstrain．theincrescenteffectofsteelfiberon

thestrainatpeaktensileloadismoreremarkable．

3．2．2Tensileworkandtoughnessmodulus

Thetensileworkwasdefinedastheareaundertheload-displacementcurvefrom0to0．5rain．More—over，atensiletoughnessmoduluswasintroduced（showninTable5）．

Itwasdefinedas：

（2）

where，fftistheultimatetensilestrengthofSFRC；A，theareaofthecrosssectionofspecimen．

BoththesetwoparameterswerequotedtoevaluatethetoughnesscharactersofSFRCunderuniaxialtension．Thetensiletoughnessmodulusisadimensionlessfactor．Comparedtowhatthetensileworkdoes．itcanavoidtheinfluenceoftheultimatetensilestrengthwhenstudyingthetoughnessofSFRC．

ItcallbefoundfromTable5thatthealteringregularitiesofthesetwofactorsalongwiththechangesofmatrixstrengthandfibercontentareapproximate．Therefore，theemphasisofanalysiswasputonthetoughnessmodulus．

TherelationshipbetweenthematrixstrengthandtoughnessmodulusofSFRCwithfourkindsofsteelfiberareshowninFig．3．whosefibercontentsareall1．O％byvolume．togetherwiththatrelationshipofplainconcrete．ThetensiletoughnessofSFRCismuchbetterthanthatofplainconcrete．Thetensiletougheningeffectofsteelfiberisremarkable．Asthematrixstrengthrises．Thebrittlenessofconcreteincreasesobviously，andthenthete