建筑学外文文献Word下载.docx

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1ProjectEngineer,ThorntonTomasetti,51MadisonAve.,Floor17,NewYork,NY10010.

2Professor,Dept.ofArchitecturalEngineering,PennsylvaniaStateUniv.,104EngineeringUnitA,UniversityPark,PA16802.

（Accepted17June2010;

publishedonline15February2011）

Introductiontop

Theuseofsteelstudbackupwallforbrickveneersystemshasbeenontheriseduringthepreviousthreedecades.Thereasonsfortheincreasedpopularityofsteelstudbackupwallsystemsincludereducedweight,costsavings,andshorterconstructiontime.However,therearesomeproblemswiththebrickveneeroversteelstud（BV/SS）backupwallsystem.Unlikeconcretemasonryunit（CMU）backupwalls,light-gaugesteelstudsusedinbackupsystemsareveryflexible.Therefore,theycanhavealargedeflectionunderastrongwindloadleadingtothecrackingofthebrickveneer（BV）.Wind-drivenraincanpotentiallypenetratethecrackedBVandcorrodethemetaltiesandsteelstuds（SS）.Because,inmostsystems,tiesaretheonlyconnectionsbetweentheBVandthesteelstudbackup（SSB）,corrodedtiescanleadtoahazardousfailureoftheBVunderhighwindloadorotherout-of-planeloadingsituations.

ConventionalBVoverbothCMUbackupwallsandSSBsystemsmayalsohavepotentialproblemsduringearthquakes.Inbothsystems,gapsundertheshelfanglesserveashorizontalmovementjointsandaresupposedtopreventtheBVfromparticipatinginthein-planeseismicloadresistance.However,duringrecentearthquakes,somewallsfailedorcrackedasaresultofin-planeseismicforces.OnemajorreasonforthispoorperformanceisattributabletotheclosureofthegapsasaresultofthedifferentialmovementoftheBVandthebackup.Thismovementjoint,actingasanisolationmechanism,canmalfunction,andasaresult,BVwallsmaycrackorfailbecauseofthein-planeseismicforces.

Thesefailures,togetherwithaslowrateofconstructioncausedbytheextratimeneededtolaybricksanderectscaffoldingatthejobsite,areconsideredtheshortcomingsofaconventionalBV/SSsystem.Toimprovetheseissues,theconceptofaprefabricatedandpanelizedBVwithasteelframeworkbackupwallsystemwasdevelopedatthePennsylvaniaStateUniversity.Forbrevity,thesystemwillbereferredtoasapanelizedbrickveneeroversteelstud（PBVSS）backupwallsysteminthispaper.Thepilotresearchprogramconsistedofthedesignanddevelopmentofthesystemthatincludedtheconsiderationofthebuildingscience-relatedissues,athree-dimensional（3D）finite-elementmodelingandanalysis,afull-scalesimulatedwind-loadingtest,andafull-scaleseismicrackingtesttoevaluatetheperformanceoftheproposedPBVSSdesign.DetailsoftheentireresearchprogramweredescribedinLiang（200632）;

thispaperdiscussesthebuildingscience-relatedresearchresultsafterintroducingthedesignfeaturesoftheproposedPBVSSsystem.

LiteratureReviewofMajorIssueswithConventionalSystemandOverviewofPanelizedSystemstop

AnchoredBVoverbackupwallsystemscanbedesignedmoreefficientlythansingle-wythemasonrybarrierwallstokeepwind-drivenrainwateroutofthebuildingandtoallowtheplacementofinsulationboardsinsidethewallcavity（DrysdaleandSuter199115）.TheBVwithbackupwallsystemsmainlyservethreefunctionsinbuildings:

structuralfunctions,screenfunctions,andcomfortfunctions（DrysdaleandSuter199115;

Kroger200529;

StraubeandBurnett200546）.Toprovidethesefunctions,thefollowingcomponentsareincludedinmostdesignsofBVwithbackupwallsystems[BrickIndustryAssociation（BIA）19998;

Devalapuraetal.199613;

DrysdaleandHamid200814;

DrysdaleandSutter199115;

Grimm199322;

Hatzinikolasetal.198525;

KPFFConsultingEngineers199828;

TheMasonryStandardsJointCommittee（MSJC）200235]:

veneer,backupwallandframe,sheathing,ties,aircavity,shelfangle,movementjoints,thermalinsulation,vaporretarder,airbarrier,flashing,andweepholes.

Thefailureofunreinforcedmasonry（URM）buildingsandofsomeBVwallsinearthquakesandtornadoswithlife-safetyhazards;

aswellasproblemsrelatedtorainwaterpenetration,corrosionofmasonrytiesandanchorbolts,visiblecrackingofthebrickveneer,andbowingofthewall;

havebeenreported[Brock19969;

Cowie199012;

EarthquakeEngineeringResearchInstitute（EERI）199016,199517,200118;

Hageletal.200723;

Hamidetal.198524;

Jaliletal.199326;

LaBelle200430;

McGinleyandErnest200438;

PetersonandShelton200942;

Schulatzetal.199945].OneoftheprimaryreasonsforthepoorperformanceofBVwallsystemsisthattheyaregenerallyconsideredas“nonstructural”wallsthatarenotdesignedtoparticipateinresistinggravityandlateralloads,whereasinreality,theyparticipatetosomedegreeunlesspropertyisolated.Amisunderstandingofthestructuralfunctionandtheimportanceoftheload-bearingroleofBVwallshasledtothefailureofthesesystems.AccordingtoSchindler（200444）,inadequateattentiontothenonstructuralintentoftheconstructiondetailsforisolationpurposeshasbeenacommonsourceofproblems.Moreover,asimpleserviceabilityproblemsuchaswaterleakagethroughaBVwallcanleadtothecorrosionoftiesandanchorboltsandresultinalife-safetyhazardduringhighwindorevenduringamoderateearthquakesituation.

CurrentearthquakedesigndetailsforanchoredBVwallscallforhorizontalmovementjointsundershelfanglestoaccommodateinterstorylateraldrifts.Thesmallgapundertheshelfangleisprovidedtoaccommodatethedifferentialverticaldeformationattributabletotemperature,creep,andmoisturebetweentheclayBVandthestructuralframe.Ifconstructedproperly,thisgapcanalsofunctionasahorizontalisolationjointallowingstorydriftswithoutrestrainingtheBVwalls.However,insomeexistingbuildings,thismovementjointwaspoorlyconstructed,andarecentstudy（Memarietal.2002a39,b40）hasdescribedthepotentialdamageduringearthquakesbecauseoftheabsenceofthegaporbecauseoftheclosureofthegapbymortar.

Adesignassumptionforout-of-planewind-loadingonBV/SSisthattheBVwillcrackbecausetheSSBwallismoreflexiblethantheBV（ChenandTrestain200410）.Whentiesarecorroded,theout-of-planeresistanceoftheBVunderhighwindloadsorearthquakeeventswilllikelybejeopardizedwithpotentialfalloutconsequences.OnthebasisofGrimm’sliteraturereview（199221）,therecommendationbysomedesignersistouseaheavyconcretemasonrybackupwalltoavoidtheproblemsassociatedwithaconventionalBV/SSsystem.However,suchadesignwilllosetheadvantagesthatlightweightSSBwallscanoffer.Therefore,totakeadvantageoftheweightsavingsofBV/SSwallsystemsinseismicregions,aninnovativedesignofBVwallsystemsshouldaddressthepotentialproblemsunderbothhighwindandseismicloadingconditions.

BVproblemsarenotlimitedtoperformance-relatedissuesunderenvironmentalandotherloadingconditions.Onecanstillseemasonsonscaffoldingseveralstorieshighlayingbricksone-by-one.Reportsofscaffoldingfailuresattributabletovariouscausesincludingexcessivebrickweightandscaffoldingconnectionfailuresthatresultincasualtiesarenotscarce（Gonchar200120）.TheconstructionmethodforBValsohasroomforimprovement.

Thebuilt-on-sitecharacterofbrickworkmakesitsconstructionhighlydependentontheweatheranditsqualitycontrolrelativelydifficult.Onesolutiontosuchproblemsistopanelizeandprefabricatethebrickwallconstruction（Tawresey200448）.Concretewallpanelswithembeddedthinbricksandprecastconcretecladdingwithafacethatlookslikeabrickwallhavebeencommerciallyprefabricated（Anderson19966）.Althoughsomewallmanufacturerscancastconcretepanelswithavarietyoffaceshelltexturesincludingbricklikepatterns,manyownersandarchitectswouldstillliketouserealexteriorclayBVwallsbecauseoftheiraestheticallypleasingappearance.LindowandJasinski（200333）describedapanelizedBVwallsystemforwhichthebackupwall,insulation,andshelfanglewereassembledasapanelatthefactory,andtheBVwythewasconstructedatthejobsite.Moreover,itispossibletodevelopaprefabricatedclayBVwithoutabackupwallsystembyusingverticalsteelreinforcement（Palmer199941）orbyemployingposttensioning（LaursenandIngham200031）.Louis（199934）describedmanyoftheissuesthatshouldbeconsideredinthedevelopmentofprefabricatedbrickwallpanelsincludingveneerwallpanels.AlthoughinpanelizedBVwallsthebrickstillhastobelaidone-by-one,theprocesscanalwaysbedoneonthegroundinthecontrolledenvironmentofafabricationplant.Workerswillnothavetolaybricksatahighelevation.Themanufacturingprocessisnotinfluencedbyharshweatherlikerain,snow,orextremelylowtemperature.Continuousproductionisguaranteed,andthetotalerectiontimecanbedecreasedbyupto75%（LindowandJasinski200333）.

Thepanelizationofwallsalsomakesitpossibletoadoptbetterseismicisolationconnections.ConventionalBVaresupposedtobeisolatedfromtheseismicmovementsofthemainframethroughhorizontalmovementjointsundertheshelfangles.However,themovementjointsmaybeclosedbydifferentialmovementsorconstructionerrorcausingtheBVtobeinvolvedduringin-planeseismicforceresistance.Toreducethepotentialforsuchproblemsinconventionalsystems,perhapsthedesignprofessionalshouldrequireacloseinspectionofallhorizontalmovementjointsaspartoftheapproval