土木工程外文文献及翻译同名6070.docx

土木工程外文文献及翻译同名6070.docx

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土木工程外文文献及翻译同名6070

土木工程外文文献及翻译（同名6070）

本科毕业设计

外文文献及译文

文献、资料题目：

DesigningAgainstFireOfBuilding

文献、资料来源：

国道数据库

文献、资料发表（出版）日期：

2008.3.25

院（部）：

土木工程学院

专业：

土木工程

班级：

土木辅修091

姓名：

武建伟

学号：

2008121008

指导教师：

周学军、李相云

翻译日期：

20012.6.1

requirements.Attheoutset,itneedstobenotedthatdesigningabuildingforfiresafetyisfarmorethansimplyconsideringthebuildingstructureandwhetherithassufficientstructuraladequacy.Thisisbecausefirescanhaveadirectinfluenceonoccupantsviasmokeandheatandcangrowinsizeandseverityunlikeothereffectsimposedonthebuilding.Notwithstandingthesecomments,thefocusofthispaperwillbelargelyondesignissuesassociatedwiththebuildingstructure.

Twosituationsassociatedwithabuildingareusedforthepurposeofdiscussion.Themulti-storeyofficebuildingshowninFigure1issupportedbyatransferstructurethatspansoverasetofrailwaytracks.Itisassumedthatawiderangeofrailtrafficutilisesthesetracksincludingfreightanddiesellocomotives.Thefirstsituationtobeconsideredfromafiresafetyperspectiveisthetransferstructure.ThisistermedSituation1andthekeyquestionsare:

whatleveloffireresistanceisrequiredforthistransferstructureandhowcanthisbedetermined?

Thissituationhasbeenchosensinceitclearlyfallsoutsidethenormalregulatoryscopeofmostbuild-ingregulations.Anengineeringsolution,ratherthanaprescriptiveoneisrequired.Thesecondfiresituation（termedSituation2）correspondstoafirewithintheofficelevelsofthebuildingandiscoveredbybuildingregulations.Thissituationischosenbecauseitwillenableadiscussionofengineeringapproachesandhowtheseinterfacewiththebuildingregulations–sincebothengineeringandprescriptivesolutionsarepossible.

2UNIQUENESSOFFIRE

2.1Introduction

Windandearthquakescanbeconsideredtobe“natural”phenomenaoverwhichdesignershavenocontrolexceptperhapstochoosethelocationofbuildingsmorecarefullyonthebasisofhistoricalrecordsandtodesignbuildingtoresistsufficientlyhighloadsoraccelerationsfortheparticularlocation.Deadandliveloadsinbuildingsaretheresultofgravity.Alloftheseloadsarevariableanditispossible（althoughgenerallyunlikely）thattheloadsmayexceedtheresistanceofthecriticalstructuralmembersresultinginstructuralfailure.

Thenatureandinfluenceoffiresinbuildingsarequitedifferenttothoseassociatedwithother“loads”towhichabuildingmaybesubjectedto.Theessentialdifferencesaredescribedinthefollowingsections.

2.2OriginofFire

Inmostsituations（ignoringbushfires）,fireoriginatesfromhumanactivitieswithinthebuildingorthemalfunctionofequipmentplacedwithinthebuildingtoprovideaserviceableenvironment.Itfollowsthereforethatitispossibletoinfluencetherateoffirestartsbyinfluencinghumanbehaviour,limitingandmonitoringhumanbehaviourandimprovingthedesignofequipmentanditsmaintenance.Thisisnotthecasefortheusualloadsappliedtoabuilding.

2.3AbilitytoInfluence

Sincewindandearthquakearedirectlyfunctionsofnature,itisnotpossibletoinfluencesucheventstoanyextent.Onehastoanticipatethemanddesignaccordingly.Itmaybepossibletoinfluencethelevelofliveloadinabuildingbyconductingauditsandplacingrestrictionsoncontents.However,inthecaseofafirestart,therearemanyfactorsthatcanbebroughttobeartoinfluencetheultimatesizeofthefireanditseffectwithinthebuilding.Itisknownthatoccupantswithinabuildingwilloftendetectafireanddealwithitbeforeitreachesasig-nificantsize.Itisestimatedthatlessthanonefireinfive（Favre,1996）resultsinacalltothefirebrigadeandforfiresreportedtothefirebrigade,themajoritywillbelimitedtotheroomoffireorigin.Inoc-cupiedspaces,olfactorycues（smell）providepowerfulevidenceofthepresenceofevenasmallfire.Theadditionofafunctionalsmokedetectionsystemwillfurtherimprovethelikelihoodofdetectionandofactionbeingtakenbytheoccupants.

Firefightingequipment,suchasextinguishersandhosereels,isgenerallyprovidedwithinbuildingsfortheuseofoccupantsandmanyorganisationsprovidetrainingforstaffinrespectoftheuseofsuchequipment.

Thegrowthofafirecanalsobelimitedbyautomaticextinguishingsystemssuchassprinklers,whichcanbedesignedtohavehighlevelsofeffectiveness.Firescanalsobelimitedbythefirebrigadedependingonthesizeandlocationofthefireatthetimeofarrival.

2.4EffectsofFire

Thestructuralelementsinthevicinityofthefirewillexperiencetheeffectsofheat.Thetemperatureswithinthestructuralelementswillincreasewithtimeofexposuretothefire,therateoftemperaturerisebeingdictatedbythethermalresistanceofthestructuralelementandtheseverityofthefire.Theincreaseintemperatureswithinamemberwillresultinboththermalexpansionand,eventually,areductioninthestructuralresistanceofthemember.Differentialthermalexpansionwillleadtobowingofamember.Significantaxialexpansionwillbeaccommodatedinsteelmembersbyeitheroverallorlocalbucklingoryieldingoflocal-isedregions.Theseeffectswillbedetrimentalforcolumnsbutforbeamsformingpartofafloorsystemmayassistinthedevelopmentofotherloadresistingmechanisms（seeSection4.3.5）.

Withtheexceptionofthedevelopmentofforcesduetorestraintofthermalexpansion,firedoesnotimposeloadsonthestructurebutratherreducesstiffnessandstrength.Sucheffectsarenotinstantaneousbutareafunctionoftimeandthisisdifferenttotheeffectsofloadssuchasearthquakeandwindthataremoreorlessinstantaneous.

Heatingeffectsassociatedwithafirewillnotbesignificantortherateoflossofcapacitywillbeslowedif:

（a）thefireisextinguished（e.g.aneffectivesprinklersystem）

（b）thefireisofinsufficientseverity–insufficientfuel,and/or

（c）thestructuralelementshavesufficientthermalmassand/orinsulationtoslowtheriseininternaltemperature

Fireprotectionmeasuressuchasprovidingsufficientaxisdistanceanddimensionsforconcreteelements,andsufficientinsulationthicknessforsteelelementsareexamplesof（c）.TheseareillustratedinFigure2.

Thetwosituationsdescribedintheintroductionarenowconsidered.

3FIREWITHINBUILDINGS

3.1FireSafetyConsiderations

Theimplicationsoffirewithintheoccupiedpartsoftheofficebuilding（Figure1）（Situation2）arenowconsidered.Firestatisticsforofficebuildingsshowthataboutonefatalityisexpectedinanofficebuildingforevery1000firesreportedtothefirebrigade.Thisisanorderofmagnitudelessthanthefatalityrateassociatedwithapartmentbuildings.Morethantwothirdsoffiresoccurduringoccupiedhoursandthisisduetothegreaterhumanactivityandthegreateruseofserviceswithinthebuilding.Itistwiceaslikelythatafirethatcommencesoutofnormalworkinghourswillextendbeyondtheenclosureoffireorigin.

Arelativelysmallfirecangeneratelargequantitiesofsmokewithintheflooroffireorigin.Ifthefloorisofopen-planconstructionwithfewpartitions,thepresenceofafireduringnormaloccupiedhoursisalmostcertaintobedetectedthroughtheobservationofsmokeonthefloor.Thepresenceoffullheightpartitionsacrossthefloorwillslowthespreadofsmokeandpossiblyalsothespeedatwhichtheoccupantsdetectthefire.Anymeasuresaimedatimprovinghousekeeping,fireawarenessandfireresponsewillbebeneficialinreducingthelikelihoodofmajorfiresduringoccupiedhours.

Formulti-storeybuildings,smokedetectionsystemsandalarmsareoftenprovidedtogive“automatic”detectionandwarningtotheoccupants.Analarmsignalisalsotransmittedtothefirebrigade.

Shouldthefirenotbeabletobecontrolledbytheoccupantsonthefirefloor,theywillneedtoleavetheflooroffireoriginviathestairs.Stairenclosuresmaybedesignedtobefire-resistantbutthismaynotbesufficienttokeepthesmokeoutofthestairs.Manybuildingsincorporatestairpressurisationsystemswherebypositiveairflowisintroducedintothestairsupondetectionofsmokewithinthebuilding.However,thisincreasestheforcesrequiredtoopenthestairdoorsandmakesitincreasinglydifficulttoaccessthestairs.Itisquitelikelythatexcessivedooropeningforceswillexist（Fazioetal,2006）

Fromafireperspective,itiscommontoconsiderthatabuildingconsistsofenclosuresformedbythepresenceofwallsandfloors.Anenclosurethathassufficientlyfire-resistantboundaries（i.e.wallsandfloors）isconsideredtoconstituteafirecompartmentandtobecapableoflimitingthespreadoffiretoanadjacentcompartment.However,theabilityofsuchboundariestorestrictthespreadoffirecanbeseverelylimitedbytheneedtoprovidenaturallighting（windows）andaccessopeningsbetweentheadjacentcompartments（doorsandstairs）.Firespreadviatheexternalopenings（windows）isadistinctpossibilitygivenafullydevelopedfire.Limit-ingthewindowsizesandgeometrycanreducebutnoteliminatethepossibilityofverticalfirespread.

Byfarthemosteffectivemeasureinlimitingfirespread,otherthanthepresenceofoccupants,isaneffectivesprinklersystemthatdeliverswatertoagrowingfirerapidlyreducingtheheatbeinggeneratedandvirtuallyextinguishingit.

3.2EstimatingFireSeverity

Intheabsenceofmeasurestoextinguishdevelopingfires,orshouldsuchsystemsfail;severefirescandevelopwithinbuildings.

Infireengineeringliterature,the