学士六层框架办公楼设计施工图实习报告外文翻译-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.

单轴拉伸试验下砖的实验研究摘要转化是来自在一个材料样本和结构逐步减少机械阻力的过程，这是粘土砖、砂浆、石材等准脆性材料具体到一个渐进过程的显著特点。其破坏的原因是内部裂纹的增长。由于缺陷和空洞的存在，这些特性通常材料的异质性。在混凝土中，拉伸破坏现象已得到确定，但是这种破坏很少存在粘土砖中。在目前的论文中，米尼奥大学进行了一系列拉伸试验，改试验还包括三个不同类型砖的单轴拉伸。这三种试验保过抗拉强度、断裂能量的量化和实用价值采纳的建议。引言混凝土和其它准脆性材料懒神行为有一个无序的内部结构材料，如砖。改象可以很好地描述最初有希勒勒提出的去裂纹模型，改模型已经作为最基本的模型用于解释准脆性材料的非线性断裂。依据这个模型，准脆性材料的一个特点就是开裂的位置不同，这是拉伸材料在不同部位的拉伸特点，见图1。直到达到高峰负荷，弹塑性应力应变关系图是有效的。据悉，非弹性行为的高峰值发生是由于微裂过程中消耗的能量通常被忽略。应力开裂张拉位移关系图1b介绍了在断裂过程区的应变后峰转化行为。凝聚力应力张开位移座高峰压力逐渐减少直到为零，与其相对应的裂纹的两个边之间距离增加从零到关键的开裂点。软化图在描述假设的基础性作用断裂过程抗拉强度特点的断裂能量，即由该地区给予的软化图，简图16.关键性裂纹张拉可以代替延性指数D；其代表了能源正常化的抗性强度。此参数允许脆性材料的表征和和降部分的形状直接关系到应力变形图。已经有几个用于测量断裂性能的实验方法对材料直接拉伸实验和间接拉伸实验本构关系，这意味着直接拉伸不是破坏的唯一原因。直接拉伸实验似乎是最适合的测试表征准脆性材料的实效机理。这个测试定义为可参考的方法。样本组织和测试程序已经在过去发表过，即测试设备，控制方法，线性可变位移传感器的安放位置。后者在图2中心理问题的相关性，在图2的案例中，用固定压板，弯矩和多个裂缝会出现。这样的结果产生于一个稍大的抗拉强度和更高的能量值消散。最后，其指出虽然抗拉强度和断裂在属性材料内考虑，但是，众所周知，砌体成分断裂依赖于大小和规模，即单位砂浆设备接口一个实验程序使用三种类型砖在文献中体现目标数据的增加。拉伸断裂参数的砖石成分，即单位和砂浆设备接口，是关键参数先进的砖石结构的数值模拟并为砖石结构的特性有更深入的了解。我在本论文中，实验程序使用三种类型的粘土砖讨论，文献提供的目标数据的增加的。测试设置的标本由河谷达拉进行的实心砖的拉伸实验，左右的砖都是挤压的，他们测试是直的，厚的，水平的和长度方向六大系列。表1给出了砖的尺寸和自由水吸收。砖的净抗压强度在沿挤出方向分别是78N/mm2，82N/mm2和5882N/mm2。在这里需指出：这些指标仅仅是指标性的，正如前两个值是从相互独立的不同研究者和不充足信息的实验程序得到的，第三个抗拉强度值是制造商提供的。值得注意的是：HP砖平行较大的尺寸，HP和HS砖在表面上有小槽以增加附着力之间的单位和支持结构。图1一般的凝聚力模型：（a）弹性应力应变图；（b）应力裂纹张开位移图图2边界条件的影响：（a）针截边界；（b）夹紧边界：（c）软化形状的影响图3为测试选择的砖：（a）砖瓦；（b）惠普砖；（c）恒生转表1砖标本系列：尺寸和吸收检测设备和应用测量设备在米尼奥大学土木工程系实验室进行的实验，使用了CS7400-S剪测试机器，这个机器有两个独立的液压执行机构，垂直位置和水平位置。其