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土木建筑外文翻译外文文献英文文献消防自动喷水灭火系统抗震设计精品文档28页
TheEvolutionofSeismicDesignofFireSprinklerSystems
RussellP.Fleming,P.E.
ExecutiveVicePresident
NationalFireSprinklerAssociation
Patterson,NY
SpecialfiresprinklersysteminstallationguidanceintendedtoguardagainstdamageduetoearthquakesfirstappearedintheNorthAmericansprinklerinstallationstandardin1947,andwaslargelybasedonexperienceintheLongBeachearthquakeof1930.AtthattimemanybuildingcodesinuseintheUnitedStatesdidnotevenaddressthesubjectofearthquakes.InsurancereportsoftheLongBeachearthquakehadindicated90damagedsprinklersystems.Thefirstguidance,containedonlyintheappendix,calledfor1to2inchesclearancearoundpipes,flexiblecouplingsinrisersand“someformoflateralandlongitudinalbracing”forfeedandcrossmains.
Inthe1951editionrequirementswereplacedinthebodyofthestandardforplacementof
longitudinalandlateralbraceswithspacingindicatedas“30to40ft”,amaximum
slendernessratioofbracemembersof200,andflexiblecouplingsonriserswhereitwas
necessarytoprotectsystemsagainstearthquakes.Thestatedintentwastolaterallybrace
for50%ofweightofwater-filledpipingandattachments.
Inthedecadessincethendeliberateeffortshavebeenmadetoclarifytherulesand
improveprotectionwithinthetextofNFPA13–InstallationofSprinklerSystems,but
alwayswiththeintentofaddressing“how”systemsaretobeprotectedagainst
earthquakes,not“where”suchprotectionistobeprovided.Itwasrecognizedthat
buildingcodesandotherauthoritiesmadethebasicdecisionswithregardtothelocation
ofearthquake-proneareas.
AlthoughtheearliestguidancecontainedinNFPA13camefromtheinsuranceindustry
inthewesternstates,theNFPACommitteeonAutomaticSprinklersformedan
EarthquakeProtectionSubcommitteein1985.Oneofthegoalsofthissubcommitteewas
todevelopameanstoaddressthebracingofsprinklersystemsinthesamemannerthat
theapplicationofsystemhydraulicshadbeenaccomplished.Althoughacomplex
subject,itwasbelievedthatmanyofthedesignaspectscouldbepre-engineeredinto
tablesandthenproperlyappliedbythetechnicianswhonormallylayoutanddetailfire
sprinklersystems.The1983standardcontainednoinformationonthesizingorfastening
ofbracingrelativetoloads.Amethodwasproposedin1984whereby“zonesof
influence”couldbeevaluatedtodeterminetotalloadsforproposedbracelocations.
Tableswereproposedfordeterminingmaximumbraceloadsandallowablefastenerloads
basedonsixdifferentcombinationsofbraceandfastenerorientationandanglefrom
vertical.
Thisconceptandtheaccompanyingtableswereacceptedintotheappendixof
thestandardinthe1987edition,andinthe1989editionthetableswereexpandedtonine
combinationsoforientationandangleandmovedintothebodyofthestandard.
2007StructuresCongress:
NewHorizonsandBetterPractices©2007ASCE
CopyrightASCE2007StructuresCongress2007
Downloaded06Mar2009to202.118.74.100.RedistributionsubjecttoASCElicenseorcopyright;seehttp:
//ascelibrary.orgTheNFPA13EarthquakeProtectionSubcommitteewasinplaceatthetimeoftheLoma
PrietaandNorthridgeearthquakesin1989and1994,andheldpublichearingsin
cooperationwiththeNationalFireSprinklerAssociationandtheSocietyofFire
ProtectionEngineersfollowingthoseeventsinordertoevaluatehowfiresprinkler
systemsperformedduringtheearthquakesandstodevelopsuggestionsforimprovements
totheprotectioncriteriawithinthestandard.
Ingeneral,theperformanceoffiresprinklersystemsinthoseearthquakeswasjudgedtobegood,withastrongcorrelationbetweenobservedfailuresanddeparturesfromtherulesofNFPA13.Oneareaacknowledgedtobeinneedofimprovementwastheinteractionofsprinklersandceilings;impactofsprinklersagainstrigidceilingsresultedinaseveralhigh-profileincidentsinwhichanumberofsprinklersopenedandwaterdamageresulted.In1999theNFPAsprinklerprojectwasreorganized.ResponsibilitiesfortheearthquakeprotectionrulesweregiventoanewNFPATechnicalCommitteeonHangingandBracingofWater-BasedFireProtectionSystems,oneoffourseparatetechnicalcommitteescoordinatedthroughaTechnicalCorrelatingCommitteeresponsibleforNFPA13.Thisallowedthedirectinputofmoreearthquakeengineeringexpertiseintothestandarddevelopmentprocess.
Majorchangesinbuildingcoderequirementsforearthquakeprotectionhavetakenplaceinthepasttwentyyears,mainlyduetotheNationalEarthquakeHazardsReductionProgram(NEHRP)provisionsdevelopedwithfundingfromtheFederalEmergencyManagementAgency.TheNEHRPprovisionsinitiallyfoundtheirwayintothecodes
throughdirectadoption,andmorerecentlythroughreferencetotheAmericanSocietyofCivilEngineer’sstandardASCE/SEI7.Asaresult,thegoalofthecommitteethatpreparesNFPA13hasevolvedduringtheyears.Fromtheoriginalgoalofindependentlyprovidingameansofprotectingsprinklersystemsagainstearthquakeforces,thecommitteeinrecentyearshasbeentryingtokeeppacewithamovingtargetassuccessiveeditionsofASCE/SEI7addressprotectionofarchitecturalandmechanicalsystems.
ThereisadifficulttransitionperiodtakingplacerightnowinvolvingtheseismicprovisionsofNFPA13andthe2003editionoftheInternationalBuildingCode®(IBC).BecauseofthereferencetoASCE/SEI7,the2003IBCdoesnotcontainthedetailedseismicrequirementsthathadbeenincludedinthe2000editionoftheIBC.Althoughgeneralreferencetothe1999editionofNFPA13iscontainedinthe2003IBC,asectionofASCE/SEI7thatmadespecialreferencetotheuseofNFPA13forearthquake
protectionwasomittedduringtheadoptionprocess,leadingsometobelievethat
sprinklerpipingmustbeprotectedthesameasothermechanicalpiping.However,
sprinklersystempipingisnotarrangedlikeothermechanicalpipingsystems,andsome
oftherulesofNFPA13havebeenspecificallydevelopedtopreventsystemdamage
duringearthquakemovement.Forexample,whilemostmechanicalpipingsupportedby
hangerrodslessthan12in.(400mm)inlengthisexemptfrombracingundercurrent
codes,comparativeexperienceofsprinklersystemswiththatexemptionversustheNFPA
exemptionofonly6in(150m)wasprovidedbythe1987NewZealandearthquake.The
2007StructuresCongress:
NewHorizonsandBetterPractices©2007ASCE
CopyrightASCE2007StructuresCongress2007
Downloaded06Mar2009to202.118.74.100.RedistributionsubjecttoASCElicenseorcopyright;seehttp:
//ascelibrary.orggeneralconclusionwasthatsystemsinstalledinaccordancewithNFPA13withstoodthe
earthquake,whilethosenotsodesignedfailed.
Overthepasttwodecadestherehavebeenanumerousrefinementsinthelanguageof
NFPA13thatreflectthelessonslearnedinearthquakesaswellastheinfluenceofthe
NEHRPprovisions.Thesecanbeevaluatedbylookingathowthevarioussectionsof
NFPA13haveevolvedintwentykeyareas:
1.ApplicabilityofNFPA13EarthquakeProtectionProvisions
1983-Wheresubjecttoearthquakes
1996-Whensprinklersystems…aretobeprotectedagainstdamagefromearthquakes
1999-Wheresprinklersystemsorabovegroundfireservicemainsarerequiredtobe
protectedagainstdamagefromearthquakes
2002-Wherewater-basedfireprotectionsystemsarerequiredtobeprotectedagainst
damagefromearthquakes
2.GeneralIntentofEarthquakeProtectionProvisions
1983-Minimizeorpreventpipebreakage
1991-Preventpipebreakage
1999-Protectagainstdamage
3.FlexibleCouplings-General
1983-Forpiping3½in.orlarger
1994-Forpiping2½in.orlarger;“Flexiblelistedpipecoupling”definedas“alisted
couplingorfittingthatallowsaxialdisplacement,rotation,andatleast1degree
ofangularmovementofthepipewithoutinducingharmonthepipe”(minimum
0.5degreesfor8-in.andlarger)
2007-Flexiblecouplingsandclearanceidentifiedasaddressingdisplacementdueto
storydrift
4.FlexibleCouplingsforRisersinMulti-StoryBuildings
1983-Atceilingofeachintermediatefloor
1994-Within12in.aboveandbelowthefloorinmultistorybuildingssuchthatthe
flexiblecouplingbelowthefloorisbelowthemainsupplyingthatfloor
2007StructuresCongress:
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CopyrightASCE2007StructuresCongress2007
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//ascelibrary.org
1999-Within12in.aboveandwithin24in.belowthefloorinmultistorybuildings;
Additionalcouplingrequiredonverticalportionoftie-inpipingwheretie-inis
belowtheupperflexiblecouplingontheriser
2007-Additionalflexiblecouplingcanbeprovidedeitherontheverticalportionoftie-in
pipingorwithin24in.onhorizontaltie-inpiping
5.DropstoHoseLines,SprinklersinRacks,andPortionsofSystems
1983-Fittingswithflexiblejointsatthetopofdropstohoselines(regardlessofsize);
Swingjointsassembledwithflexiblefittingsondropstoracksover3in.
1987-Flexiblecouplingsatthetopofdropstohoselines(regardlessofsize);Swing
jointswithflexiblefittingsondropstoracks(regardlessofsize)
1989-Flexiblecouplingatthetopofdropstohoselines,racksprinklersandmezzanines
(regardlessofsize);Flexiblecouplingatthetopofdropsexceeding15ft.to
sprinklersorportionsofsystems(regardlessofsize)
1991-Flexiblecouplingwithin24in.ofthe
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