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Storm Shelters: Selecting Design Criteria FEBRUARY 2007 TORNADO RECOVERY ADVISORY FEMA DR 1679 RA2

Purpose and Intended Audience TheintendedaudienceforthisTornadoRecoveryAdvisory isanyoneinvolvedintheplanning,policy-making,design, construction,orapprovalofshelters,includingdesigners, emergencymanagers,publicofficials,policyordecision­makers,buildingcodeofficials,andhomeorbuildingowners. HomeownersandrentersshouldalsorefertotheTornado RecoveryAdvisorytitledResidential Sheltering: In-Residence and Stand-Alone Shelter.Thepurposeofthisadvisoryisto identifythedifferenttypesofshelterdesignguidance,code requirements,andothercriteriathatpertaintothedesignand constructionofsheltersfortornadoesandhurricanes.Thereare variousstormsheltercriteria,eachofwhichoffersdifferentlevels ofprotectiontoitsshelteroccupants.

This Recovery Advisory Addresses:

Howshelterconstructionisdifferentfromtypicalbuilding construction

Structuralsystems Windbornedebrisresistance

Designcriteriafordifferenttypesofshelters

Shelterconsiderations

Seethese2007TornadoRecovery Advisoriesforinformation abouttornadorisk,sheltering fromtornadoes,andimproving manufacturedhomesagainst damagefromhighwinds:

TornadoRisksandHazardsin theSoutheasternUnitedStates (TornadoRecoveryAdvisoryNo.1)

ResidentialSheltering:In-ResidenceandStand-Alone Shelters(TornadoRecovery AdvisoryNo.3)

UnderstandingandImproving PerformanceofOlder ManufacturedHomesinHigh-Wind Events(TornadoRecoveryAdvisory No.4)

UnderstandingandImproving PerformanceofNewManufactured HomesinHigh-WindEvents (TornadoRecoveryAdvisoryNo.5)

Usefullinksandshelterresources

How Shelter Construction is Different from Typical Building Construction Ashelteristypicallyaninteriorroom,spacewithinabuilding,oranentirelyseparatebuilding,designedand constructedtoprotectitsoccupantsfromtornadoesorhurricanes.Sheltersareintendedtoprovideprotection againstbothwindforcesandtheimpactofwindbornedebris.Thelevelofoccupantprotectionprovidedby aspacespecificallydesignedasashelterisintendedtobemuchgreaterthantheprotectionprovidedby buildingsthatcomplywiththeminimumrequirementsofbuildingcodes.Themodelbuildingcodesdonot providedesignandconstructioncriteriaforlifesafetyforshelteringnordotheyprovidedesigncriteriafor tornadoes.

Shelterstypicallyfallintotwocategories:residentialsheltersandcommunity(non-residential)shelters.

Therearetwogeneraltypesofresidentialshelters:in-residence sheltersandshelterslocatedadjacentto,ornear,aresidence. Anin-residence shelter,alsocalleda“saferoom,”isasmall, speciallydesigned(“hardened”)room,suchasabathroomor closetthatisintendedtoprovideaplaceofrefugeforthepeople wholiveinthehouse.Anexternal residential shelterissimilar infunctionanddesign,butitisaseparatestructureinstalled outsidethehouse,eitheraboveorbelowground.Referalsoto theTornadoRecoveryAdvisorytitledResidential Sheltering: In-

Theterm“hardened”refersto specializeddesignandconstruction appliedtoaroomorbuildingto allowittoresistwindpressures andwindbornedebrisimpacts duringahigh-windeventandserve asashelter.

Residence and Stand-Alone Shelter.

Storm Shelters: Selecting Design Criteria HSFEHQ-07-J-0006/April 2007 Page � of 6

Acommunity shelterisintendedtoprovide protectionforalargenumberofpeople,anywhere fromapproximately12toasmanyasseveral hundredindividuals.Thesesheltersinclude notonlypublicsheltersbutprivatesheltersfor businessesandotherorganizations.

Structural Systems

Theprimarydifferenceinabuilding’sstructural systemwhendesignedforuseasashelter,rather thanforconventionaluse,isthemagnitudeofthe windforcesthatitisdesignedtowithstand.

Buildingsaredesignedtowithstandacertainwind speed(termed“design[basic]windspeed”)based onhistoricwindspeedsdocumentedfordifferentareasofthecountry.Thehighestdesignwindspeedused inconventionalconstructionisnearthecoastalareasoftheAtlanticandGulfCoastsandisintherangeof 140–150mph,3-secondgustinmostlocations.Bycontrast,thedesignwindspeedrecommendedbyFEMA1 forsheltersinthesesameareasisintherangeof200–250mph,3-secondgust;thisdesignwindspeedis intendedtoprovide“near-absoluteprotection.”

Windpressuresarecalculatedasafunctionofthesquareofthedesignwindspeed.Asaresult,the structuralsystemsofashelteraredesignedforforcesuptothreetimeshigherthanthoseusedfortypical buildingconstruction.Consequently,thestructuralsystemsofashelter(andtheconnectionsbetweenthem) areveryrobust.

Windborne Debris Resistance

Windbornedebris,commonlyreferredtoasmissiles,causesmanyoftheinjuriesandmuchofthedamage fromtornadoesandhurricanes.Windowsandtheglazinginexteriordoorsofconventionalbuildingsarenot requiredtoresistwindbornedebris,exceptforbuildingsinwindbornedebrisregions.2Impact-resistantglazing caneitherbelaminatedglass,polycarbonate,orshutters.TheASCE7missilecriteriaweredevelopedto minimizepropertydamageandimprovebuildingperformance;theywerenotdevelopedtoprotectoccupants.

Community storm shelter being constructed to FEMA 361 criteria in Wichita, Kansas.

Ifglazingispresentina tornadoshelter,itshould beprotectedbyaninterior-mountedshutterthatcanbe quicklyandeasilydeployed bytheshelteroccupants.

Toprovideoccupantprotection,thecriteriausedindesigningshelters includesubstantiallygreaterwindbornedebrisloads.

Theroofdeck,walls,anddoorsofconventionalconstructionarealso notrequiredbythebuildingcodetoresistwindbornedebris.However, theroofdeckandwallsaroundashelterspace,andthedoorsleading intoit,mustresistwindbornedebrisifthespaceinsideistoprovide occupantprotection.Additionalinformationregardingthedifferentlevels ofwindbornedebrisloadsisprovidedbelow.

Design Criteria for Different Types of Shelters Shelterswillprovidedifferentlevelsofprotectiondependinguponthedesigncriteriaused.Thelevelof protectionprovidedbyashelterisafunctionofthedesignwindspeed(andresultingwindpressure)usedin designingtheshelter,andofthewindbornedebrisloadcriteria.

Design wind speed and wind pressure criteria:Windpressurecriteriaaregivenbydifferentguides,codes andstandards.Windpressurecriteriaspecifyhowstrongthesheltermustbe.Thedesignwindspeedisthe majorfactorindeterminingthemagnitudeofthewindpressurethatthebuildingisdesignedtowithstand. InFEMA’sshelterpublications(seeUsefulLinksonpage3),recommendeddesignwindspeedsrange from160to250mph.The2006International Residential Codeandthe2006International Building Code, whichestablishtheminimumrequirementsforresidentialandotherbuildingconstruction,includedesign windspeedsrangingfrom90to150mphthroughoutmostofthecountry.Thetableonpages4–5provides acomparisonofshelterdesigncriteriaoptions.Thetableonpage6presentscomparativedatafortwo locationsusingthedesigncriteriapresentedonpages4–5.

1. FEMA361,Design and Construction Guidance for Community Shelters(July2000),availableonlineathttp://www.fema.gov/fima/fema361.shtm

2. ASCE7,AmericanSocietyofCivilEngineersStandard7,Minimum Design Loads for Buildings and Other Structures(2005)

Page 2 of 6 Storm Shelters: Selecting Design Criteria HSFEHQ-07-J-0006/April 2007

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Windborne debris load criteria: Thetableonpage3presentswindbornedebriscriteriagiveninvarious guides,codes,andstandards.Thetableshowsthedifferenttestmissilesandthecorrespondingmomentum theycarrywiththemastheystrikeashelter.Thefirstentriesonthistable(TornadoMissileTesting Requirements)aretheFEMAmissileguidanceforresidentialandcommunitysheltersthatprovidenear­absoluteprotection.

Tornado and Hurricane Windborne Debris Criteria Guidance, Code, or Standard

Criteria for the Design Missile Debris Test Speed

(mph) Large Missile Specimen Momentum at Impact (lbf s)

Tornado Missile Testing Requirements

FEMA320/FEMA361 100 15#2x4 68

InternationalCodeCouncil(ICC)Shelter Standard

100(maximum) 80(minimum)

15#2x4 15#2x4

68 55

Hurricane Missile Testing Requirements

FEMA320/FEMA361 100 15#2x4 68

ICCShelterStandard 102(maximum) 64(minimum)

9#2x4 9#2x4

42 26

FloridaStateEmergencyShelterProgram (SESP)Criteria

50(recommended) 34(EHPAminimum)

15#2x4 9#2x4

34 14

IBC/IRC2006,ASCE7-05,FloridaBuilding Code,ASTME1886/E1996

55 34

9#2x4 9#2x4

21 14

NOTES:

IBC/IRC–InternationalBuildingCode/InternationalResidentialCode

lbf-s–Pounds(force)seconds

Useful Links and Shelter Resources: Taking Shelter From the Storm: Building a Safe Room Inside Your House (FEMA320),FEMA,Washington,DC, SecondEdition,March2004.

Design and Construction Guidance for Community Shelters (FEMA361),FEMA,Washington,DC,July2000.

Tornado Protection: Selecting Refuge Areas in Buildings (FEMA431),FEMA,Washington,DC,November 2003.

Standard on the Design and Construction of Storm Shelters, International Code Council and the National Storm Shelter Association (ICC-500),(AnticipatedRelease)Late2007.

FEMA 320

FEMA 361

DRAFTFEMA 431

Storm Shelters: Selecting Design Criteria HSFEHQ-07-J-0006/April 2007 Page � of 6

Wind Design Coefficient Considerations�,� Debris Impact Criteria5 Remarks

FEMA �20:N/A–prescriptivedesignguidanceformaximumhazardFEMA �6�:UseFEMA361windspeedmapwithfourzones.CalculatepressuresusingASCE7methodsanduseI=1.0,Kd=1.0,ExposureC,notopographiceffects,GCpi=+/-0.55(thiswillaccountforatmosphericpressurechange[APC])

Testallshelterswiththerepresentativemissile:a15-lb2x4at100mph(horizontal)and67mph(vertical)

FEMA �20:Intentistoprovide“near-absoluteprotection.”Nocertificationisprovided.FEMA �6�:Intentistoprovide“near-absoluteprotection.”Shelteroperationsguidanceisprovided.Occupancyissuesaddressed.Wallsectiondetailsprovided.Nocertificationisprovided.

Tornado:UseFEMA361windspeedmap.CalculatepressuresusingASCE7methodsanduseI=1.0,Kd=1.0,Exposureasappropriate,notopographiceffects,GCpi=+/-0.55or+/-0.18+APCHurricane:UserevisedASCE7mapandmethodsanduseI=1.0,allotheritemsasperASCE7,noAPCconsiderationrequired.

Testshelterswithrepresentativemissile(missilespeeddependentonsitedesignwindspeed):Tornado:15-lb2x4at85–100mph(horizontal)and2/3ofthisspeed(vertical).Hurricane:9-lb2x4at68–105mph(horizontal)andalowerspeed(vertical)

Intentistoprovideastandardforthedesignandconstructionofhigh-windshelters.Willnotuseterm“near-absoluteprotection.”Occupancy,ventilation,anduseissuesarealsoaddressed.Shelteroperationsguidanceisprovidedinthecommentaryonly(commentaryisaseparatedocument—notaconsensusdocument).

Recommendsthatdesigneradd40mphtobasicwindspeedidentifiedonmap,ExposureC,I=1.15,Kd=0.85,GCpiasrequiredbydesign(typically+/-0.18),butrecommends+/-0.55fortornadoshelteruses

Inwindbornedebrisregion(120mph+):Small–peagravel;Large–9-lb2x4at34mph(horizontal),upto60feetabovegrade,butrecommends15-lb2x4at50mph(horizontal)

Thebuilding,oraportionofabuilding,isdefinedasanessentialfacilityandasashelter.Designerisrequiredtosubmitsigned/sealedstatementtobuildingdepartmentandStateofficesstatingthestructurehasbeendesignedasashelter(EHPAplusaddedrecommendedcriteria).

UsebasicwindspeedatsiteasidentifiedonFBCwindspeedmap,useexposureatsite,useI=1.15,Kd=0.85,GCpiasrequiredbydesign(typically+/-0.18)

Inwindbornedebrisregion(120mph+):Small–peagravel;Large–9-lb2x4at34mph(horizontal),upto60feetabovegrade

ThebuildingoraportionofabuildingisdefinedasanessentialfacilityandasanEHPA.Designerisrequiredtosubmitsigned/sealedstatementtobuildingdepartmentandStateofficesstatingthestructurehasbeendesignedasanEHPA.

Basedonregionalhazards,recommendationsareprovidedtoimproveandstrengthentheloadpathandtheperformanceofthebuildingexterior

Windowandglazingprotectionisrecommendedformosthurricane-proneareas,notjustareaswithabasicwindspeedof120mphandgreater

Thisprogramprovidesdesignandconstructionguidancetoimprovebuildingperformanceforhigh-windevents.Compliancewilllikelyimprovebuildingperformancebutdoesnotimplythatthebuildingissafeorthatitisappropriatetouseasashelter.

Methodisbasisofmostwindpressurecalculationmethods.Allitemsindesignprocessaresite-specific.UseI=1.15forcriticalandessentialfacilities

Inwindbornedebrisregion(120mph+):Small–peagravel;Large–9-lb2x4at34mph(horizontal),upto60feetabovegrade.Note:2006IBCrequiresthe9-lb2x4(large)missiletobetestedat55mphforcriticalandessentialfacilities

Coderequiresincreaseddesignparametersonlyforbuildingsdesignatedascriticaloressentialfacilities.

None None Providesguidanceonhowtoselectbuildingsandareasofabuildingforuseasahigh-windshelterorrefugearea.Doesnotprovideorrequireatechnicalassessmentoftheproposedshelterfacility.

Typicallytheseoldercodesprovidedahurricaneregionalfactorfordesignwindspeeds,butlittleattentionwaspaidtocomponentsandcladding

Notrequiredforallbuildings.Whererequired,theStandardBuildingCode6developedandrecommendeddebrisimpactstandardsforuseinhurricane-proneregions

Thesecodesspecifiedlimitedhazard-resistantrequirements.SomeguidancewasprovidedwithSSTD10fromSBCCIforthedesignandconstructionofbuildingsinhigh-windandhurricane-proneregions.Buildingsconstructedtotheseearlycodeswerenotrequiredtohavestructuralsystemscapableofresistingwindloads.

None None Bestavailablerefugeareasshouldbeidentifiedinallbuildingswithoutshelters.FEMA431,Tornado Protection: Selecting Refuge Areas in Buildings,providesguidancetohelpidentifythebestavailablerefugeareasinexistingbuildings.Becausebestavailablerefugeareasarenotspecificallydesignedasshelters,theiroccupantsmaybeinjuredorkilledduringatornadoorhurricane.

Wind Shelter Design and Construction Codes, Standards, Guidance Comparison Table�

Title or Name of Document Code, Reg, Standard, or Statute? Wind

Hazard Wind Map

FEMA Shelter Publications: FEMA �20Taking Shelter From the Storm: Building a Safe Room Inside Your House(1999) FEMA �6�Design and Construction Guidance for Community Shelters(2000)

FEMAguidancedocument,notacodeor standard.“BestPractice”forhigh-wind shelters

Tornadoand Hurricane

FEMA �20:Hazardmap,butwind speedsnotusedfordesign FEMA �6�:Mapwithfourwind speedzonesfordesign(windmri2is 10,000–100,000years).Thismap isoftenreferredtoasthe“FEMA 361map”

International Code Council/National Storm Shelter Association (ICC/NSSA) High Wind Shelter Standard (ICC-500) –currentlyindevelopment,tentatively availableforadoptioninJanuary2008.

Consensusstandardforshelterdesign andconstruction,availableforadoption inJanuary2008.Tobeincorporatedby referenceintothe2009IBCandIRC.

Tornadoand Hurricane

Tornado:UsesFEMA361map Hurricane:UsesrevisedASCE7 mapwithcontoursat10,000year mriwithminimumshelterdesign windspeedof160mph,maximum approximately240mph

Florida State Emergency Shelter Program (SESP)– FloridaInterpretationoftheAmericanRedCross(ARC) 4496Guidance.Note:sheltersinthiscategorywill rangefromEnhancedHurricaneProtectionArea(EHPA) recommendeddesignlevels,showninthisrow,tothe coderequirementlevels(nextrow),totheARC4496 requirements(seebelow).

GuidanceintheFBC“recommending” above-coderequirementsforEHPAs.See alsoAppendixGoftheStateEmergency ShelterProgram(SESP)reportforthe detaileddesignguidance.

Tornadoand Hurricane

FloridaBuildingCode(FBC)map, basedonASCE7(mapsbasically equivalent);mriis50–100years incoastalareasandadjustedwith importancefactor

Florida Building Code (FBC) EHPAs–code requirementsforpublic“shelters”(FBCSection 423.25).

StatewidecoderequirementsforEHPAs Hurricane FBCmap,basedonASCE7(maps basicallyequivalent);mriis50–100 yearsincoastalareasandadjusted withimportancefactor

Institute for Business and Home Safety (IBHS) Fortified Home Program–intendedasguidance toimprovetheperformanceofresidentialbuildings duringnaturalhazardevents,includinghigh-wind events–notconsideredadequateforsheltering.

Guidanceprovidedtoimproveperformance ofregular(non-shelter)buildingsinhigh winds

Tornadoand Hurricane

ASCE7ormodernStatebuilding codemap

FBC 2000 and later, International Building Code (IBC)/International Residential Code (IRC) 2000 and later/ASCE 7-98andlater.

Buildingcodeanddesignstandardsfor regular(non-shelter)buildings.Some additionalguidanceisprovidedin commentary.

Hurricane ASCEhasitsownwindspeedmap basedonhistoricalandprobabilistic data;mriis50–100yearsincoastal areasandadjustedwithimportance factor

American Red Cross (ARC ��96)Standards for Hurricane Evacuation Shelter Selection.

Guidanceforidentifyingbuildingstouseas hurricaneevacuationshelters

Hurricane None

Pre-2000 Building Codes Buildingcodeanddesignstandardsfor regular(non-shelter)buildings

Hurricane Eachoftheoldercodesusedtheir ownpublishedwindcontourmaps

Areas of Refuge/Last Resort GuidancefromFEMAandothersfor selectingbest-availablerefugeareas

Tornadoand Hurricane

None

NOTES:

1. Thewindshelterguidanceandrequirementsshownherearepresentedfromhighesttoleastamountofprotectionprovided.

2.Meanrecurrenceintervals(mri)forwindspeedsmapsareidentifiedbythecodeorstandardthatdevelopedthemap.Typically,themrifornon­shelterconstructioninnon-hurricane-proneareasis50yearsandinhurricane-proneregions,approximately100years.

Page � of 6 Storm Shelters: Selecting Design Criteria HSFEHQ-07-J-0006/April 2007

Title or Name of Document Code, Reg, Standard, or Statute?Wind

Hazard Wind Map

FEMA Shelter Publications:FEMA �20Taking Shelter From the Storm: Building a Safe Room Inside Your House(1999)FEMA �6�Design and Construction Guidance for Community Shelters(2000)

FEMAguidancedocument,notacodeorstandard.“BestPractice”forhigh-windshelters

TornadoandHurricane

FEMA �20:Hazardmap,butwindspeedsnotusedfordesignFEMA �6�:Mapwithfourwindspeedzonesfordesign(windmri2is10,000–100,000years).Thismapisoftenreferredtoasthe“FEMA361map”

International Code Council/National Storm Shelter Association (ICC/NSSA) High Wind Shelter Standard (ICC-500) –currentlyindevelopment,tentativelyavailableforadoptioninJanuary2008.

Consensusstandardforshelterdesignandconstruction,availableforadoptioninJanuary2008.Tobeincorporatedbyreferenceintothe2009IBCandIRC.

TornadoandHurricane

Tornado:UsesFEMA361mapHurricane:UsesrevisedASCE7mapwithcontoursat10,000yearmriwithminimumshelterdesignwindspeedof160mph,maximumapproximately240mph

Florida State Emergency Shelter Program (SESP)–FloridaInterpretationoftheAmericanRedCross(ARC)4496Guidance.Note:sheltersinthiscategorywillrangefromEnhancedHurricaneProtectionArea(EHPA)recommendeddesignlevels,showninthisrow,tothecoderequirementlevels(nextrow),totheARC4496requirements(seebelow).

GuidanceintheFBC“recommending”above-coderequirementsforEHPAs.SeealsoAppendixGoftheStateEmergencyShelterProgram(SESP)reportforthedetaileddesignguidance.

TornadoandHurricane

FloridaBuildingCode(FBC)map,basedonASCE7(mapsbasicallyequivalent);mriis50–100yearsincoastalareasandadjustedwithimportancefactor

Florida Building Code (FBC) EHPAs–coderequirementsforpublic“shelters”(FBCSection423.25).

StatewidecoderequirementsforEHPAs Hurricane FBCmap,basedonASCE7(mapsbasicallyequivalent);mriis50–100yearsincoastalareasandadjustedwithimportancefactor

Institute for Business and Home Safety (IBHS) Fortified Home Program–intendedasguidancetoimprovetheperformanceofresidentialbuildingsduringnaturalhazardevents,includinghigh-windevents–notconsideredadequateforsheltering.

Guidanceprovidedtoimproveperformanceofregular(non-shelter)buildingsinhighwinds

TornadoandHurricane

ASCE7ormodernStatebuildingcodemap

FBC 2000 and later, International Building Code (IBC)/International Residential Code (IRC) 2000 and later/ASCE 7-98andlater.

Buildingcodeanddesignstandardsforregular(non-shelter)buildings.Someadditionalguidanceisprovidedincommentary.

Hurricane ASCEhasitsownwindspeedmapbasedonhistoricalandprobabilisticdata;mriis50–100yearsincoastalareasandadjustedwithimportancefactor

American Red Cross (ARC ��96)Standards for Hurricane Evacuation Shelter Selection.

Guidanceforidentifyingbuildingstouseashurricaneevacuationshelters

Hurricane None

Pre-2000 Building Codes Buildingcodeanddesignstandardsforregular(non-shelter)buildings

Hurricane Eachoftheoldercodesusedtheirownpublishedwindcontourmaps

Areas of Refuge/Last Resort GuidancefromFEMAandothersforselectingbest-availablerefugeareas

TornadoandHurricane

None

Part2oftable(continuedfrompage4)

Wind Design Coefficient Considerations�,� Debris Impact Criteria5 Remarks

FEMA �20:N/A–prescriptivedesign guidanceformaximumhazard FEMA �6�:UseFEMA361windspeed mapwithfourzones.Calculatepressures usingASCE7methodsanduseI=1.0, Kd=1.0,ExposureC,notopographic effects,GCpi=+/-0.55(thiswillaccountfor atmosphericpressurechange[APC])

Testallshelterswiththerepresentative missile:a15-lb2x4at100mph (horizontal)and67mph(vertical)

FEMA �20:Intentistoprovide“near-absoluteprotection.”No certificationisprovided. FEMA �6�:Intentistoprovide“near-absoluteprotection.”Shelter operationsguidanceisprovided.Occupancyissuesaddressed. Wallsectiondetailsprovided.Nocertificationisprovided.

Tornado:UseFEMA361windspeed map.CalculatepressuresusingASCE7 methodsanduseI=1.0,Kd=1.0,Exposure asappropriate,notopographiceffects, GCpi=+/-0.55or+/-0.18+APC Hurricane:UserevisedASCE7mapand methodsanduseI=1.0,allotheritemsas perASCE7,noAPCconsiderationrequired.

Testshelterswithrepresentative missile(missilespeeddependenton sitedesignwindspeed):Tornado:15-lb 2x4at85–100mph(horizontal)and 2/3ofthisspeed(vertical).Hurricane: 9-lb2x4at68–105mph(horizontal) andalowerspeed(vertical)

Intentistoprovideastandardforthedesignandconstructionof high-windshelters.Willnotuseterm“near-absoluteprotection.” Occupancy,ventilation,anduseissuesarealsoaddressed. Shelteroperationsguidanceisprovidedinthecommentary only(commentaryisaseparatedocument—notaconsensus document).

Recommendsthatdesigneradd40mph tobasicwindspeedidentifiedonmap, ExposureC,I=1.15,Kd=0.85,GCpias requiredbydesign(typically+/-0.18),but recommends+/-0.55fortornadoshelter uses

Inwindbornedebrisregion(120 mph+):Small–peagravel;Large–9-lb 2x4at34mph(horizontal),upto60 feetabovegrade,butrecommends15­lb2x4at50mph(horizontal)

Thebuilding,oraportionofabuilding,isdefinedasanessential facilityandasashelter.Designerisrequiredtosubmitsigned/ sealedstatementtobuildingdepartmentandStateofficesstating thestructurehasbeendesignedasashelter(EHPAplusadded recommendedcriteria).

Usebasicwindspeedatsiteasidentified onFBCwindspeedmap,useexposureat site,useI=1.15,Kd=0.85,GCpiasrequired bydesign(typically+/-0.18)

Inwindbornedebrisregion(120 mph+):Small–peagravel;Large–9-lb 2x4at34mph(horizontal),upto60 feetabovegrade

Thebuildingoraportionofabuildingisdefinedasanessential facilityandasanEHPA.Designerisrequiredtosubmitsigned/ sealedstatementtobuildingdepartmentandStateofficesstating thestructurehasbeendesignedasanEHPA.

Basedonregionalhazards, recommendationsareprovidedtoimprove andstrengthentheloadpathandthe performanceofthebuildingexterior

Windowandglazingprotectionis recommendedformosthurricane-prone areas,notjustareaswithabasicwind speedof120mphandgreater

Thisprogramprovidesdesignandconstructionguidanceto improvebuildingperformanceforhigh-windevents.Compliance willlikelyimprovebuildingperformancebutdoesnotimplythatthe buildingissafeorthatitisappropriatetouseasashelter.

Methodisbasisofmostwindpressure calculationmethods.Allitemsindesign processaresite-specific.UseI=1.15for criticalandessentialfacilities

Inwindbornedebrisregion(120 mph+):Small–peagravel;Large–9-lb 2x4at34mph(horizontal),upto60 feetabovegrade. Note:2006IBCrequiresthe9-lb2x4 (large)missiletobetestedat55mph forcriticalandessentialfacilities

Coderequiresincreaseddesignparametersonlyforbuildings designatedascriticaloressentialfacilities.

None None Providesguidanceonhowtoselectbuildingsandareasofabuilding foruseasahigh-windshelterorrefugearea.Doesnotprovideor requireatechnicalassessmentoftheproposedshelterfacility.

Typicallytheseoldercodesprovideda hurricaneregionalfactorfordesignwind speeds,butlittleattentionwaspaidto componentsandcladding

Notrequiredforallbuildings.Where required,theStandardBuildingCode6 developedandrecommendeddebris impactstandardsforuseinhurricane­proneregions

Thesecodesspecifiedlimitedhazard-resistantrequirements. SomeguidancewasprovidedwithSSTD10fromSBCCIforthe designandconstructionofbuildingsinhigh-windandhurricane­proneregions.Buildingsconstructedtotheseearlycodeswerenot requiredtohavestructuralsystemscapableofresistingwindloads.

None None Bestavailablerefugeareasshouldbeidentifiedinallbuildings withoutshelters.FEMA431,Tornado Protection: Selecting Refuge Areas in Buildings,providesguidancetohelpidentifythebest availablerefugeareasinexistingbuildings.Becausebestavailable refugeareasarenotspecificallydesignedasshelters,their occupantsmaybeinjuredorkilledduringatornadoorhurricane.

NOTES(continued):

3. ASCE7-05Building Design Loads for Buildings and Other Structures(2005)istheloaddeterminationstandardreferencedbythe modelbuildingcodes.Thewinddesignproceduresusedforanysheltertypeinthistableuseoneofthewinddesignmethodsas specifiedinASCE7-05,butwithchangestocertaindesigncoefficientsthatareidentifiedbythedifferentcodes,standards,or guidancesummarizedinthistable.

4. FromASCE7method:I=importancefactor;Kd=winddirectionalityfactor;GCpi=internalpressurecofficient

5. Roofdeck,walls,doors,openings,andopeningprotectionsystemsmustallbetestedtoshowresistancetothedesignmissileforthe FEMA,ICC,andFLEHPAcriteria.

6. FromtheSouthernBuildingCodeCongressInternational,Inc.(SBCCI).

Storm Shelters: Selecting Design Criteria HSFEHQ-07-J-0006/April 2007 Page 5 of 6

Thetablebelowshowscomparativedatafortwolocationsforthedesigncriteriapresentedintheprevious table.Wherenoguidanceisprovidedforshelteringorbasicconstruction,“N/A”(notapplicable)isstated. Wheretherequirementisnotrequired,“Notrequired”isstated.

Design Criteria Comparison Shelter Design Standard,

Code, or Document Data� Example Location #�:

Miami, FL Example Location #2:

Atlanta, GA

FEMA320/361 Designwindspeed 200mph 200mph

Pressureonwindwardwall 107psf2 107psf

Pressureonroofsection 257psf(suction) 257psf(suction)

Testmissilemomentumatimpact 68lbf-s2 68lbf-s

ICC-500(pending1/08) Designwindspeed 200mph(tornado) 225mph(hurricane)

200mph(tornado) 160mph(hurricane)

Pressureonwindwardwall 107psf(tornado) 136psf(hurricane)

107psf(tornado) 69psf(hurricane)

Pressureonroofsection 257psf(tornado,suction) 325psf(hurricane,suction)

257psf(tornado,suction) 202psf(hurricane,suction)

Testmissilemomentumatimpact 68lbf-s(tornado) 42-26lbf-s(hurricane)

68lbf-s(tornado) 42-26lbf-s(hurricane)

FBCEHPA/SESP (using+40mph recommendation)

Designwindspeed 186mph 130mph

Pressureonwindwardwall 91psf 44psf

Pressureonroofsection 217psf(suction) 106psf(suction)

Testmissilemomentumatimpact 34lbf-s 34lbf-s

FBCEHPA Designwindspeed 146mph N/A

Pressureonwindwardwall 39psf N/A

Pressureonroofsection 117psf(suction) N/A

Testmissilemomentumatimpact 14lbf-s N/A

IBHS Designwindspeed 150mph 90mph

Pressureonwindwardwall 41psf 15psf

Pressureonroofsection 124psf(suction) 44psf(suction)

Testmissilemomentumatimpact 14lbf-s 14lbf-s

ASCE7-05/IBC2006 (ASTME1996)

Designwindspeed 150mph 90mph

Pressureonwindwardwall 41psf 15psf

Pressureonroofsection 124psf(suction) 44psf(suction)

Testmissilemomentumatimpact 14lbf-s Notrequired

ARC4496 Designwindspeed N/A N/A

Pressureonwindwardwall N/A N/A

Pressureonroofsection N/A N/A

Testmissilemomentumatimpact N/A N/A

Pre-2000BuildingCodes Designwindspeed 140mphandless 90mphandless

Pressureonwindwardwall <40psf(varies) <15psf(varies)

Pressureonroofsection <120psf(varies) <45psf(varies)

Testmissilemomentumatimpact Notrequiredbyallcodes Notrequired

AreasofLastResort Designwindspeed Unknown Unknown

Pressureonwindwardwall Unknown Unknown

Pressureonroofsection Unknown Unknown

Testmissilemomentumatimpact Notrequired Notrequired NOTES: 1. Windpressureswerecalculatedbasedona40-footx40-footsquarebuilding,witha10-footeaveheightanda10-degreeroofpitch. 2. psf–Poundspersquarefoot;lbf-s–Pounds(force)seconds

Page 6 of 6 Storm Shelters: Selecting Design Criteria HSFEHQ-07-J-0006/April 2007