學(xué)士六層框架辦公樓設(shè)計(jì)施工圖實(shí)習(xí)報(bào)告外文翻譯-dwg

ExperimentalInvestigationofBricksUnderUniaxialTensileTestingBSTRACTSofteningisagradualdecreaseofmechanicalresistanceresultingfromacontinuousincreaseofdeformationimposedonamaterialspecimenorstructure.Itisasalientfeatureofquasi-brittlematerialslikeclaybrick,mortar,ceramics,stoneorconcretewhichfailduetoaprocessofprogressiveInternalcrackgrowth.Suchmechanicalbehaviouriscommonlyattributedtotheheterogeneityofthematerial,duetothepresenceofdifferentphasesandmaterialdefects,suchasflawsandvoids.Fortensilefailurethisphenomenonhasbeenwellidentifiedforconcretebutveryfewresultsexistsforclaybrick..Inthepresentpaper,theresultsofanextensivesetoftestscarriedoutatUniversityofMinhoandincludingthreedifferenttypesofbackunderniaxialtensionwillbepresented.Bothtensilestrengthandfractureenergyarequantified,withrecommendationsfortheadoptionofpracticalvalues.INTRODUCTIONThetensilebehaviourofconcreteandotherquasi-brittlematerialsthathaveadisorderedInternalstructure,suchasbrick.canbewelldescribedbythecohesivecrackmodelproposedinitiallybyHILLERBORG[1].Thismodelhasbeenwidelyusedasthefundamentalmodelthatdescribesthenon-linearfracturemechanicsofquasi-brittlematerials,e.g.[2,3].Accordingtothismodelandduetocrackinglocalization,whichisacharacteristicoffractureprocessInquasi-brittlematerials,thetensilebehaviourIscharacterizedbytwoconstitutivelawsassociatedwithdifferentzonesofthematerialduringtheloadingprocess.seeFigure1.Theelastic-plasticstress-strainrelationshipofFigurelaisvaliduntilthepeakloadisreached.ItisnotedthatbeforethepeakInelasticbehaviouroccursduetomicro-crackingandtheenergydissipatedinthisprocessisusuallyneglectedforthecalculationofthefractureenergy.Thestress-crackopeningdisplacementrelationshipofFigurelbdescribesthestrainsofteningbehaviourinthefractureprocesszoneafterthepeak.Thecohesivestress-openingdisplacementdiagramIscharacterizedbythegradualdecreaseofstressfromftmaximumvalue,tozero,correspondingtotheIncreaseofthedistancebetweenthetwoedgesofthecrackfromzerotothecriticalopening,u,ThesofteningdiagramassumesafundamentalroleInthedescriptionofthefractureprocessandIscharacterizedbythetensilestrength,fr,andthefractureenergy,Gr,whichIsgivenbytheareaunderthesofteningdiagram,seeFigure1b.Thecriticalcrackopening,ue,canbereplacedbytheductilityindexd,[4]givenastheratioGrlfr,whichrepresentsthefractureenergynormalizedbythetensilestrength.Thisparameterallowsthecharacterizationofthebrittlenessofthematerialandisdirectlyrelatedtotheshapeofthedescendingportionofthestress-deformationdiagram.Thereareseveralexperimentalmethodsthathavebeenusedtomeasurethefractureproperties(tensilestrength,fractureenergyandductilityIndex)thatallowthedefinitionoftheconstitutivelawsofthematerial,namelydirecttensiletests,indirecttensiletestssuchasthethree-pointloadtest,andtheBraziliansplittingtest.Althoughtensilefailureresultsfromaloadcombinationandamultiplicity,offactors.meaningthatdirecttensionisnottheonlycauseoftensilecracking,adirecttensiletestseemstobethemoslappropriatetesttocharacterizethebasicfailuremechanism(modeI)ofquasi-brittlematerials.ThistestIsdefinedasthereferencemethodtofollow(5jbeingadoptedinthisworkfarthecharacterizationofthetensilebehaviourofbricks.Differentissuesrelatedtothespecimensandthetestprocedureshavebeendiscussedinthepast,namelythetestingequipment,thecontrolmethod,thelocationoftheLinearVariableDisplacementTransducers(LVDTs),thealignmentofthespecimenand,especially,theattachmentofthespecimenstothesteelplatens.TherelevanceofthelatterIsaddressedInFigure2[6].ThebehaviourinFigure2a(rotatingplatensorhinges)Isjustifiedbytherotationofthespecimenduringtheloadingoperation,wherethecrackproceedsfromonesideofthespecimentotheotherside.InthecaseofFigure2busingfixed(non-rotating)platens,abendingmomentisintroducedandmultiplecrackswillappear.Thisresultsinaslightlylargertensilestrengthandahighervalueofenergydissipated(fractureenergy).Finally,ItisnotedthatalthoughthetensilestrengthandfractureenergyareconsideredIntrinsicpropertiesofthematerial,itIswellknownthatfracturepropertiesaresizeandscaledependent[6,7].Tensilefractureparametersofmasonryconstituents,namelyunitsandthemortar-unitinterface,arekeyparametersforadvancednumericalmodellingofmasonryandforadeeperunderstandingofthebehaviourofmasonrystructures.inmepresentpaper,anexperimentalprogrammeusingthreetypesofclaybrickIsdiscussedwiththeobjectiveofincreasingthedataavailableintheliterature.TESTSET-UPANDSPECIMENSTensiletestswereperformedwithsolidbricksproducedbyValedaGandara,Portugal(S),hollowbricksproducedbyJ.MonteiroeFilhos,Portugal(HP),andhollowbricksproducedbySuceram,Spain(HS).Allbricksareextrudedandtheyweretestedinverticalorthickness(V)andinhorizontalorlength(H)directionresultinginsixserieswiththefollowingnotation:SV,SH;HPV,HPH;HSV,HSH.Table1givesthedimensionsofthebricksandthefreewaterabsorption.Thenetcompressivestrengthofthebricks,alongtheextrusiondirectionwas78N/mm282N/mm2and58N/mm2,respectivelyforS.HPandHS.Hereitisnotedthatthesevaluesaremerelyindicative,asthefirsttwovalueswerefromindependenttestsbydifferentresearchersandinsufficientInformationaboutthetestingproceduresisavailable,see(8,9].Thethirdvalueofcompressivestrengthwasprovidedbythemanufacturer.Itisnotedthat:(a)bricksHPareextrudedwiththeholesparalleltothelargerdimensionandbricksHSareextrudedwiththeholesparalleltothesmallerdimension;(b)bricksHPandHShavesmallgroovesintheuppersurface(sideoppositetothefacingside)inordertoincreaseadhesionbetweentheunitandthebackingmortar,seeFlgure3.TestingequipmentandappliedmeasuringdevicesThetestswereperformedinthelaboratoryoftheCivilEngineeringDepartmentofUniversityofMinho,usingaCS7400-Sshearingtestingmachine.Thismachinehastwoindependenthydraulicactuators,positionedinverticalandhorizontaldirections.Ithasaloadcellconnectedtotheverticalactuatorwithamaximumcapacityof25kN,beingparticularlysuitedtosmallspecimens(maximumsizeof90x150x150mm).Theadoptionofaconstantcrosssectionforthespecimensleadstouncertaintyaboutthelocationofthemicro-cracks.Thisrepresentstheusualsupplementarydifficultyforthecontrolmethodofthistypeoftest.SincethecontrolsystemallowsonlyoneLinearVariableDisplacementTransducer(LVDT)asdisplacementcontrol,itwasdecidedtointroduce,bymeansadiamondsawingmachine,twolateralnotcheswithadepthof8mmandathicknessof3mmatmidheightofthespecimeninordertolocalizethefracturesurface.Withthenotches,thestressanddeformationdistributionisnolongeruniform,withstressandstraingradientsoccurringverylocalizednearthenotchtips.Sincethree-dimensionalnpn-uniformcrackopeningcanoccurontensiletests[10],thetensiletestcontrolusingtheaverageofthedeformationsregisteredonthefourcornersofthespecimenisthemostappropriateprocedure,seeFigure4.However,theavailableequipmentcanonlycontrolonedisplacementtransducer(LVDT),locatedatanotchedside.Thetransducershaveameasurebaseof1mmwithalinearityof0.17%ofthefullstroke.Adeformationrateof0.5um/swasusedinthetests.Theforceappliedwasmeasuredonaloadcellof25kNmaximumloadbearingcapacity,withanaccuracyof0.03%.Afterpreparationofthespecimens'ends,glueadhesionconditionswereenhancedbymakingaseriesofsuperficialslotswithasaw.Then,thespecimenswerecarefullyfixedtothesteelplatensusinganepoxyresin(DEVCOM)insuchawaythattheplatenswerekeptperfectlyparallel.Here,ItIsnotedthatthesteelplatensarefixed(non-rotating),meaningthatloadeccentricityIsnotspecimens.Theonlysourceofanissueforpnsmadceccentricityisparallelismbetweenthesteelplatenswhichwethelackof,uldinduceabendingmomentInthespecimenintheclampingoperation.SpecimendimensionsTakingintoconsiderationthebrickdimensionsandthetestset-up,40x40x70mmSbrickspecimenswereextractedasshownInFigure5.HPandHSbricksarehollowand,therefore,thespecimensextractedfromthebricksmustberepresentativeofthebrickshell,achannelorUspecimens,andthebrickweb1specimens,seeFigure6.Here,itisnotedthattheusageofchannelspecimensinquestionablebecausealoadeccentricityisintroducedbythefactthetopandbottomflangesarefullygluedtothesteelspecimens.Nevertheless,becausetheendplatensarefullyfixed,theeccentricityisverylow.alinearelasticFEMcalculationIndicatesthatthenormalizedloadeccentricity(measuredbyeccentricity/webwidth)isonly0.03.RESULTSFromtheforce-elongationrelationshipobtainedinthetensiletests,thefollowingparameterswereevaluated:tensilestrength,fractureenergy,andresidualstressatultimatescanreading.ThenotchesreducetheYoung'smodulusofthebrick(Eb)byabout20%-40%[11].AsthemeasureofEbisquestionable,itisnotshownhere.Figure7illustratestheprocedureadoptedforevaluatingthefractureenergy,G,.Inthecohesivecrackmodeladdressedabove,thecrackopeninguisequaltothetotalelongation,subtractedfromtheelasticdeformation(u,,=vxlmaes/E0)andtheirreversibledeformationu;,,,whichaccountsforinelasticeffectsduringmaterialunloading,inthevicinityofthemacro-crack.Here,/meansisthedistancebetweenthemeasuringpointsoftheLVDT.Themaximumforcerecordedbytheloadcellwasdividedbytheeffectiveareaofeachspecimen(notchedcross-section),inordertodeterminethetensilestrength.Thefractureenergyisidentifiedwiththeworkthatiscarriedouttocompletetheseparationofthetwofacesofthemacro-crack,perunitofarea.Itisnotpossibletodeterminetheexactcrackopeningforwhichthestressvaluetransferredbecomeszero,duetolongtailexhibitedbythesofteningbranchofthestress-openingcrack.Forthecalculationofthefractureenergy,thevalueofthefractureenergyIsusuallycalculatedastheresultofthesumoftwoquantities,onequantitybeingmeasuredandtheotherquantityestimated.ThemeasuredvalueoffractureenergyGf,meansisdirectlycomputedastheareaunderthestress-crackopeningdiagramuptoanominalvalueofthepeakstrength(ortheultimatevalue).TheestimatedvalueGi,&iscalculatedastheareaunderthelinearcurveobtainedbylinear[12]ornon-linear[11]adjustmentoftheoriginaldiagrambelowthecut-off.Here,takingintoaccounttheforce-elongationdiagramsandtheinternalfrictionofthetestingequipment,thefractureenergywassimplyevaluateduptoadeflectionof60pmoruptoadeflectioncorrespondingtoaforceof200N(ifthedeflectionislessthan60pm).Forthetestsabortedbeforetheselimitconditions,theenergydissipatedwasnotevaluated.SspecimensThestress-elongationrelationshipsforspecimensSVFigure8.ForspecimensSV(intheextrusiondirection),theaveragevaluesWere3.48N/mm2(42%)forthetensilestrengthand0.0575N/mm(39%)forthefractureenergy.Theductilityindex,againgivenbytheratioGf/ft,was0.0165mm.ThevaluesinsidebracketsIndicatethevaluesofthecoefficients(CV)forthesixteensuccessfultests.ForspecimensSH(perpendiclartotheextrusiondirection),theaveragevalueswere2.96N/mm(63%)forthetensilestrengthand0.0508N/mm(41%)forthefractureenergy.Thevaluesinsidebracketsindicatethevaluesofthecoefficientsofvariationforthefourteensuccessfultests.Theductilityindexwas0.0172mm..Thetensilestrengthintheextrusiondirectionwas4.5%ofthecompressivestrength.Thetensilestrengthintheextrusiondirectionwas18%higherandthefractureenergyis15%higherthanthevaluesobtainedintheperpendiculardirection,duetothealignmentofthemicrostructure.Theductilitywassimilarinbothdirections.Therefore,bricktypeSexhibitedonlymoderateanisotropy.Alltheresultsexhibitveryalargescatter,thoughthescatterwashigherinthedirectionperpendiculartotheextrusiondirection.Thereasonforthisseemstobeflaws,micro-cracksandinclusionsintheburntclay.Itiswellknownthatthefractureprocessisathree-dimensionalprocess[10]andFigure9aillustratesthetypicalsuperficialcrackingpatternsofbrickspecimens.ItisclearthatbothstraightandpronouncedS-shapedcracksappear,meaningthatalargescattermustbefound.Inallcases,thecrackingsurfacewastortuous,goingaroundtheaggregateandconcentratingintheinterfacesbetweentheaggregateandthematrix.Finally,theresultsofthefractureenergyvs.thetensilestrengthwereplottedinFigure10,whereitcanbeseenthattherewasaweakcorrelationbetweenfractureenergyandtensilestrength,althoughacleartrendforfractureenergytoincreasewithanincreaseoftensilestrengthwasfound.CUNGLUSIONThepresentpaperaimstodiscussthetensilebehaviourofbricksandprovidedataforadvancednumericalsimulations.Forthispurpose,threedifferentproducerswereselectedincludingsolidandhollowbricksfromPortugalandSpain.Directtensiletestsonaservo-controlledmachinewerecarriedoutinordertoobtainthetensilestrength,thefractureenergyandtheshapeofthestress-elongationdiagram.Allbricksweretestedintwoorthogonaldirections,namelyalongandnormaltothedirectionofextrusion.Forthehollowbricks,twodifferenttypesofspecimenwereextractedsothattheshellandthewebcouldbecharacterized.Duetothepresenceofvoidsandinternalfiringcracks,thecompletestress-elongationdiagramcouldnotbeobtainedinseveralofthespecimens.Theresultsindicatealargescatterforthetensilestrengthandfractureenergy.Thefolldwingconclusionswithrespecttothetensilestrengtharepossible:(a)brickspossessanisotropywithhigherstrengthinthedirectionparalleltoextrusion;(b)inhollowbricks,thetensilestrengthoftheshellishigherthanthatoftheweb.Moreover,theaverageresultsinthebrickspecimensarefairlyconstanttakingintoconsiderationthatthreedifferentbrickmanufacturerswereinvolved.Therefore,forpracticalpurposesthefollowingrecommendationsseempossible:(a)thetensilestrengthofbrickisaround5%ofthecompressivestrength(withvaluesfoundaround4N/mm2inthedirectionparalleltoextrusionand3N/mm2inthedirectionperpendiculartoextrusion);(b)theductilityindexisaround0.018mm(meaningthatthefractureenergyfoundisaround0.08and0.06N/mm,respectivelyparallelandperpendiculartotheextrusiondirection).Thevaluesfoundapplysolelyforsolidbricksandmustbereducedforhollowbricks,accordingtothevolumeofholes.ACKNOWLEDGMENTSThepresentworkwaspartiallysupportedbyprojectGROW-1999-70420"Industrialisedsolutionsforconstructionofreinforcedbrickmasonryshellroofs"fundedbyEuropeanCommission.

單軸拉伸試驗(yàn)下磚的實(shí)驗(yàn)研究摘要轉(zhuǎn)化是來(lái)自在一個(gè)材料樣本和結(jié)構(gòu)逐步減少機(jī)械阻力的過(guò)程，這是粘土磚、砂漿、石材等準(zhǔn)脆性材料具體到一個(gè)漸進(jìn)過(guò)程的顯著特點(diǎn)。其破壞的原因是內(nèi)部裂紋的增長(zhǎng)。由于缺陷和空洞的存在，這些特性通常材料的異質(zhì)性。在混凝土中，拉伸破壞現(xiàn)象已得到確定，但是這種破壞很少存在粘土磚中。在目前的論文中，米尼奧大學(xué)進(jìn)行了一系列拉伸試驗(yàn)，改試驗(yàn)還包括三個(gè)不同類型磚的單軸拉伸。這三種試驗(yàn)保過(guò)抗拉強(qiáng)度、斷裂能量的量化和實(shí)用價(jià)值采納的建議。引言混凝土和其它準(zhǔn)脆性材料懶神行為有一個(gè)無(wú)序的內(nèi)部結(jié)構(gòu)材料，如磚。改象可以很好地描述最初有希勒勒提出的去裂紋模型，改模型已經(jīng)作為最基本的模型用于解釋準(zhǔn)脆性材料的非線性斷裂。依據(jù)這個(gè)模型，準(zhǔn)脆性材料的一個(gè)特點(diǎn)就是開(kāi)裂的位置不同，這是拉伸材料在不同部位的拉伸特點(diǎn)，見(jiàn)圖1。直到達(dá)到高峰負(fù)荷，彈塑性應(yīng)力應(yīng)變關(guān)系圖是有效的。據(jù)悉，非彈性行為的高峰值發(fā)生是由于微裂過(guò)程中消耗的能量通常被忽略。應(yīng)力開(kāi)裂張拉位移關(guān)系圖1b介紹了在斷裂過(guò)程區(qū)的應(yīng)變后峰轉(zhuǎn)化行為。凝聚力應(yīng)力張開(kāi)位移座高峰壓力逐漸減少直到為零，與其相對(duì)應(yīng)的裂紋的兩個(gè)邊之間距離增加從零到關(guān)鍵的開(kāi)裂點(diǎn)。軟化圖在描述假設(shè)的基礎(chǔ)性作用斷裂過(guò)程抗拉強(qiáng)度特點(diǎn)的斷裂能量，即由該地區(qū)給予的軟化圖，簡(jiǎn)圖16.關(guān)鍵性裂紋張拉可以代替延性指數(shù)D；其代表了能源正?；目剐詮?qiáng)度。此參數(shù)允許脆性材料的表征和和降部分的形狀直接關(guān)系到應(yīng)力變形圖。已經(jīng)有幾個(gè)用于測(cè)量斷裂性能的實(shí)驗(yàn)方法對(duì)材料直接拉伸實(shí)驗(yàn)和間接拉伸實(shí)驗(yàn)本構(gòu)關(guān)系，這意味著直接拉伸不是破壞的唯一原因。直接拉伸實(shí)驗(yàn)似乎是最適合的測(cè)試表征準(zhǔn)脆性材料的實(shí)效機(jī)理。這個(gè)測(cè)試定義為可參考的方法。樣本組織和測(cè)試程序已經(jīng)在過(guò)去發(fā)表過(guò)，即測(cè)試設(shè)備，控制方法，線性可變位移傳感器的安放位置。后者在圖2中心理問(wèn)題的相關(guān)性，在圖2的案例中，用固定壓板，彎矩和多個(gè)裂縫會(huì)出現(xiàn)。這樣的結(jié)果產(chǎn)生于一個(gè)稍大的抗拉強(qiáng)度和更高的能量值消散。最后，其指出雖然抗拉強(qiáng)度和斷裂在屬性材料內(nèi)考慮，但是，眾所周知，砌體成分?jǐn)嗔岩蕾囉诖笮『鸵?guī)模，即單位砂漿設(shè)備接口一個(gè)實(shí)驗(yàn)程序使用三種類型磚在文獻(xiàn)中體現(xiàn)目標(biāo)數(shù)據(jù)的增加。拉伸斷裂參數(shù)的磚石成分，即單位和砂漿設(shè)備接口，是關(guān)鍵參數(shù)先進(jìn)的磚石結(jié)構(gòu)的數(shù)值模擬并為磚石結(jié)構(gòu)的特性有更深入的了解。我在本論文中，實(shí)驗(yàn)程序使用三種類型的粘土磚討論，文獻(xiàn)提供的目標(biāo)數(shù)據(jù)的增加的。測(cè)試設(shè)置的標(biāo)本由河谷達(dá)拉進(jìn)行的實(shí)心磚的拉伸實(shí)驗(yàn)，左右的磚都是擠壓的，他們測(cè)試是直的，厚的，水平的和長(zhǎng)度方向六大系列。表1給出了磚的尺寸和自由水吸收。磚的凈抗壓強(qiáng)度在沿?cái)D出方向分別是78N/mm2，82N/mm2和5882N/mm2。在這里需指出：這些指標(biāo)僅僅是指標(biāo)性的，正如前兩個(gè)值是從相互獨(dú)立的不同研究者和不充足信息的實(shí)驗(yàn)程序得到的，第三個(gè)抗拉強(qiáng)度值是制造商提供的。值得注意的是：HP磚平行較大的尺寸，HP和HS磚在表面上有小槽以增加附著力之間的單位和支持結(jié)構(gòu)。圖1一般的凝聚力模型：（a）彈性應(yīng)力應(yīng)變圖；（b）應(yīng)力裂紋張開(kāi)位移圖圖2邊界條件的影響：（a）針截邊界；（b）夾緊邊界：（c）軟化形狀的影響圖3為測(cè)試選擇的磚：（a）磚瓦；（b）惠普磚；（c）恒生轉(zhuǎn)表1磚標(biāo)本系列：尺寸和吸收檢測(cè)設(shè)備和應(yīng)用測(cè)量設(shè)備在米尼奧大學(xué)土木工程系實(shí)驗(yàn)室進(jìn)行的實(shí)驗(yàn)，使用了CS7400-S剪測(cè)試機(jī)器，這個(gè)機(jī)器有兩個(gè)獨(dú)立的液壓執(zhí)行機(jī)構(gòu)，垂直位置和水平位置。其