建筑类外文翻翻译Word格式文档下载.docx
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建筑类外文翻翻译Word格式文档下载.docx
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Constructionsystems
Havingconsideredthechallengepresentedbyglobalwarmingandtheopportunitiestogeneratefossil-freeenergy,itisnowtimetoconsiderhowthedemandsideoftheenergyequationcanrespondtothatchallenge.Thebuiltenvironmentisthegreatestsectoralconsumerofenergyand,withinthatsector,housingisinpolepositionaccountingfor28percentofallUKcarbondioxide(CO2)emissions.
IntheUKhousinghastraditionallybeenofmasonryandsincetheearly1920sthishaslargelybeenofcavityconstruction.Thepurposewastoensurethatasaturatedexternalleafwouldhavenophysicalcontactwiththeinnerleafapartfromwalltiesandthatwaterwouldbedischargedthroughweepholesatthedamp-proofcourselevel.Sincetheintroductionofthermalregulations,initiallydeemednecessarytoconserveenergyratherthantheplanet,ithasbeencommonpracticetointroduceinsulationintothecavity.Foralongtimeitwasmandatorytopreserveaspacewithinthecavityandalongrearguardbattlewasfoughtbythetraditionaliststopreservethis‘sacredspace’.DefeatwasfinallyconcededwhensomeextensiveresearchbytheBuildingResearchEstablishmentfoundthattherewasnogreaterriskofdamppenetrationwithfilledcavitiesandinfactdampthroughcondensationwasreduced.
SolidmasonrywallswithexternalinsulationarecommonpracticeincontinentalEuropeandarebeginningtomakeanappearanceintheUK.InCornwallthePenwithHousingAssociationhasbuiltapartmentsofthisconstructionontheseafront,perhapsthemostchallengingofsituations.
Theadvantagesofmasonryconstructionare:
●Itisatriedandtestedtechnologyfamiliartohousebuildingcompaniesofallsizes.
●Itisdurableandgenerallyriskfreeasregardscatastrophicfailure–thoughnotentirely.AfewyearsagotheentireouterleafofauniversitybuildinginPlymouthcollapsedduetothefactthatthewalltieshadcorroded.
●Exposedbrickworkisalowmaintenancesystem;
maintenancedemandsriseconsiderablyifitreceivesarenderedfinish.
●Fromtheenergyefficiencypointofview,masonryhomeshavearelativelyhighthermalmasswhichisconsiderablyimprovediftherearehighdensitymasonryinternalwallsandconcretefloors.
Framedconstruction
Volumehousebuildersareincreasinglyresortingtotimber-framedconstructionwithabrickouterskin,makingthemappearidenticaltofullmasonryconstruction.Theattractionisthespeedoferectionespeciallywhenelementsarefabricatedoffsite.However,thereisanunfortunatehistorybehindthissystemduetoshortcomingsinqualitycontrol.Thiscanapplytotimberwhichhasnotbeenadequatelycuredorseasoned.Framedbuildingsneedtohaveavapourbarriertowallsaswellasroofs.Withtimberframingitisdifficulttoavoidpiercingthebarrier.Therecanalsobeproblemsachievinginternalfixings.Forthepurist,theultimatecriticismisthatitisillogicaltohaveaframedbuildingcladinmasonrywhenitcriesoutforapanel,boarded,slateortilehungexternalfinish.
Pressedsteelframesforhomesarenowbeingvigorouslypromotedbythesteelindustry.Thesellingpointisagainspeedoferectionbutwiththeaddedbenefitofaguaranteedqualityintermsofstrengthanddurabilityofthematerial.
Fromtheenergypointofview,framedbuildingscanaccommodatehighlevelsofinsulationbuthaverelativelypoorthermalmassunlessthisisprovidedbyfloorsandinternalwalls.
Innovativetechniques
PermanentInsulationFormworkSystems(PIFS)arebeginningtomakeanappearanceinBritain.TheprinciplebehindPIFSistheuseofprecisionmouldedinterlockinghollowblocksmadefromaninsulationmaterial,usuallyexpandedpolystyrene.Theycanberapidlyassembledonsiteandthenfilledwithpumpgradeconcrete.Whentheconcretehassettheresultisahighlyinsulatedwallreadyfortheinstallationofservicesandinternalandexteriorfinishes.TheycanachieveaU-valueaslowas0.11W/m2K.Abovethreestoreystheadditionofsteelreinforcementisnecessary.
Theadvantagesofthissystemare:
●Designflexibility;
almostanyplanshapeispossible.
●Easeandspeedoferection;
skillrequirementsaremodestwhichiswhyithasprovedpopularwiththeself-buildsector.Experiencederectorscanachieve5m2permanhourforerectionandplacementofconcrete.
●Thefinishedproducthashighstructuralstrengthtogetherwithconsiderablethermalmassandhighinsulationvalue.
Solardesign
Passivesolardesign
Sincethesundriveseveryaspectoftheclimateitislogicaltodescribethetechniquesadoptedinbuildingstotakeadvantageofthisfactas‘solardesign’.Themostbasicresponseisreferredtoas‘passivesolardesign’.Inthiscasebuildingsaredesignedtotakefulladvantageofsolargainwithoutanyintermediateoperations.
Accesstosolarradiationisdeterminedbyanumberofconditions:
●thesun’spositionrelativetotheprincipalfacadesofthebuilding(solaraltitudeandazimuth);
●siteorientationandslope;
●existingobstructionsonthesite;
●potentialforovershadowingfromobstructionsoutsidethesiteboundary.
Oneofthemethodsbywhichsolaraccesscanbeevaluatedistheuseofsomeformofsunchart.Mostoftenusedisthestereographicsunchartinwhichaseriesofradiatinglinesandconcentriccirclesallowthepositionofnearbyobstructionstoinsolation,suchasotherbuildings,tobeplotted.Onthesamechartaseriesofsunpathtrajectoriesarealsodrawn(usuallyonearcforthe21stdayofeachmonth);
alsomarkedarethetimesoftheday.Theintersectionoftheobstructions’outlinesandthesolartrajectoriesindicatetimesoftransitionbetweensunlightandshade.Normallyadifferentchartisconstructedforuseatdifferentlatitudes(atabouttwodegreeintervals).
Sunlightandshadepatternscastbytheproposedbuildingitselfshouldalsobeconsidered.Graphicalandcomputerpredictiontechniquesmaybeemployedaswellastechniquessuchasthetestingofphysicalmodelswithaheliodon.
ComputermodellingofshadowscastbythesunfromanypositionisofferedbyIntegratedEnvironmentalSolutions(IES)withits‘Suncast’program.Thisisauser-friendlyprogramwhichshouldbewellwithinnormalundergraduatecompetence.
Thespacingbetweenbuildingsisimportantifovershadingistobeavoidedduringwintermonthswhenthebenefitofsolarheatgainreachesitspeak.Onslopingsitesthereisacriticalrelationshipbetweentheangleofslopeandthelevelofovershading.Forexample,ifovershadingistobeavoidedatalatitudeof50_N,rowsofhousesona10_north-facingslopemustbemorethantwiceasfarapartthanon
10_south-facingslope.
Treescanobviouslyobstructsunlight.However,iftheyaredeciduous,theyperformthedualfunctionofpermittingsolarpenetrationduringthewinterwhilstprovidingadegreeofshadinginthesummer.
Againspacingbetweentreesandbuildingsiscritical.
Passivesolardesigncanbedividedintothreebroadcategories:
●directgain;
●indirectgain;
●attachedsunspaceorconservatory.
Eachofthethreecategoriesreliesinadifferentwayonthe‘greenhouseeffect’asameansofabsorbingandretainingheat.Thegreenhouseeffectinbuildingsisthatprocesswhichismimickedbyglobalenvironmentalwarming.Inbuildings,theincidentsolarradiationistransmittedbyfacadeglazingtotheinteriorwhereitisabsorbedbytheinternalsurfacescausingwarming.However,re-emissionofheatbackthroughtheglazingisblockedbythefactthattheradiationisofamuchlonger
wavelengththantheincomingradiation.Thisisbecausethere-emissionisfromsurfacesatamuchlowertemperatureandtheglazingreflectsbacksuchradiationtotheinterior.
Directgain
Directgainisthedesigntechniqueinwhichoneattemptstoconcentratethemajorityofthebuilding’sglazingonthesun-facingfacade.Solarradiationisadmitteddirectlyintothespaceconcerned.Twoexamples30yearsapartaretheauthor’shouseinSheffield,designedin1967andtheHockertonProjectof1998byRobertandBrendaVale.Themaindesigncharacteristicsare:
●Aperturesthroughwhichsunlightisadmittedshouldbeonthesolarsideofthebuilding,withinabout30_ofsouthforthenorthernhemisphere.
●Windowsfacingwestmayposeasummeroverheatingrisk.
●Windowsshouldbeatleastdoubleglazedwithlowemissivityglass(LowE)asnowrequiredbytheUKBuildingRegulations.
●Themainoccupiedlivingspacesshouldbelocatedonthesolarsideofthebuilding.
●Thefloorshouldbeofahighthermalmasstoabsorbtheheatandprovidethermalinertia,whichreducestemperaturefluctuationsinsidethebuilding.
●Asregardsthebenefitsofthermalmass,forthenormaldailycycleofheatabsorptionandemission,itisonlyaboutthefirst100mmofthicknesswhichisinvolvedinthestorageprocess.Thicknessgreaterthanthisprovidesmarginalimprovementsinperformancebutcanbeusefulinsomelonger-termstorageoptions.
●Inthecaseofsolidfloors,insulationshouldbebeneat
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