updated building codes

7/27/2019 Updated Building Codes

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UpdatedBuildingCodesAreChangingBatteryRackCertificationRequirements

DesignandTestingImpacts

KenSabo

SeniorProductManager

Aptus

Montclair,CA

91763

AbstractBuildingcodesaffectingSeismicBatteryRackshavechangedsignificantlyoverthepast10yearsintheUnited

States.ThesimpleUBCZone14(UniformBuildingCode)systemthatmosthistoricVLArackswerebuilttono

longerapplies,havingbeenreplacedbythemorecomplexIBC(InternationalBuildingCode).TheIBCcodeis

moredifficulttounderstand,havingmanyparametersthatinfluencewhatisasitecompliantseismicrating.

Thesefactorsmakeitdifficulttoknowifahistoricrackmeetsthenewcoderequirementsandhowtodesignfor

maximummarketcoverageandminimalcost.StateandlocalmunicipalcodesliketheCBC(CaliforniaBuilding

Code)andOSHPD(OfficeofStatewideHealthPlanningandDevelopment)

introduceadditionalrequirements

thatimpactthedesignandoverallcostofracksystems.IndustrystandardssuchasIEEE693(Instituteof

Electricaland

Electronics

Engineers)

can

influence

rack

design

and

qualification

as

well.

Combine

the

changes

thesevariouscodesintroducewiththeACI31805(AmericanConcreteInstitute)changesfortheanchoringof

structuresandanewcriteriahasbeenestablishedforsitecompliantbatteryrackingsystems.

ThechangesinanchoringrequirementsperACI31805,wherethecodenowrequiresthemetalanchoror

structuretoyieldpriortotheconcrete,isimpactinghowracksareinstalled.Longeranchorsorotheranchoring

designsarebeingrequiredandhistoricanchoringschemesonracksmaybeinsufficient.

Theapplicablechangesinthebuildingcodesandtheirimpactonbatteryrackdesignsarereviewed.IBC2012

coderequirements,includingASCE710Section13(AmericanSocietyofCivilEngineers),areintroducedalong

withtheincreasedrequirementforshaketabletesting,especiallyasitappliestoessentialfacilitiescompliance.

OSHPDand

IEEE

693

are

reviewed

to

highlight

the

impact

of

market

specific

requirements

to

design.

UniformBuildingCode(UBC)Forover30years,designingbatteryracksforcomplianceandcertificationtoUBCearthquakeloadrequirements

wasrelativelysimpleforthemarkettounderstand.TheUBCcodedefinedfourprimaryseismiczonecategories

numbered14withasimplisticmapoftheUStodeterminewherethesezoneswereandwasabroadbrush

approachfordeterminingtheseismicrequirementsforstructures.Batteryrackscouldbecertifiedbyanalysis,

onlyhavingtherequirementthattheybesignedandstampedbyacertifiedProfessionalEngineer(PE)tobe

acceptedinthemarketplace.Inadditiontodefiningwhichzonetheinstallationsitewasin,twootherfactors

wereneededtodeterminewhichrackdesignwasacceptableforuseatasite,thesefactorsarewhetherthe

facilityisclassifiedasanEssentialFacility(i.e.mustremainoperationalaftertheearthquake)andwhetherthe

installationis

at/below

grade

or

above

grade.

Higher

load

factors

were

applied

in

the

analysis

for

an

Essential

facilityclassificationorabovegradeclassification.ForSpecifyingEngineersandRackDesigners,rack

classificationsweredefinedbyansweringthefollowingquestions:

1.WhatZoneistheracktobeinstalledin?

2.IstheinstallationinanEssentialFacility?

3.Istheinstallationabovegradelevelorisitat/belowgrade?

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IBCCodeFactorsWhenengineersarespecifyingparametersforIBCratedrackingsystems,avarietyoftermsareincludedinthe

specifications.Someareapplicableandsomearenot.Listedbelowarethetypicalparametersthatmaybeina

rackspecificationfordefiningtheIBCrequirements:

SS=ShortTermAcceleration(0.2sec),obtainedforthesitefromtheUSGSSSSpectralAcceleration

Map.ThisvalueappliestoRackingsystemsthatareshortandvibratehigherfrequencies.

S1=MappedAccelerationsfor1sec,obtainedforthesitefromtheUSGS1SSpectralAccelerationMap.

Thisvalueappliestotallerbuildingsthatvibrateatlowfrequencies,andisnotusedintherackanalysis.

SiteClass(SoilFactors)AthroughFvaluesthatdetermineloadfactorsappliedtotheSS/S1values.The

factorsareclassifiedforIBCinaccordancewithASCE7,Chapter20.ThedefaultforIBCanalysesif

unknownisSiteClassD(StiffSoil)whichwillbeonmostgenericspecifications.

SDSFivepercentdampeddesignspectralresponseaccelerationatshortperiods,SS RiskCategory(2012)orOccupancyClass(20002009)DefinedinRomannumeralsItoIV.CategoryIV

isequivalenttothehistoricalEssentialFacilityClassification.RiskCategoryandSDSvaluesdefinethe

SeismicDesignCategoryforASCE7.

z/h:Factorforwheretherackislocatedinthebuildingasapercentageofbuildingheight

o 0.0=at/belowgrade

o

1.0=top

of

building

OnlySS,SiteClass,RiskCategoryandLocationinbuildingarerequiredtodefinetherackrequirements.

TheSDSvaluesandotherinformationfromtheIBCcodeisthenloadedintotheASCE7,Chapter13equationsfor

earthquakeloadingtogeneratethenecessaryFPvalues,theDesignAccelerationsings,tobeusedinthe

analysisorshaketabletests.ASCE7istheprimaryforceloadingdocumentreferencedbyIBC.Sinceracksarea

steelconstructiontheAmericanInstituteofSteelConstructioncodeAISC360isalsoreferencedinIBC.

RackanchoringdesignrequirementswithinIBCaredefinedbytheAmericanConcreteInstitutesACI318

standardsandarecommentedoninafollowingsection.

IBCImpactonRackDesignLightorLowSeismicRacks(SimilartoUBCZone2racks)

HistoricUBCZone2B,essential,abovegradecertifiedrackstendtomeetmostoftherequirementsforlight

seismicIBClevelswithminimalchanges,aslongastheresultantforceglevelsaresimilar.DefiningtheexactIBC

parametersthatlightseismicracksshouldbedesignedtoisoneofthebiggestchallengeforrack

manufacturers,sincenoconsistentstandardhasbeensetforthisrange.SinceIBCdefinesanSSinapercentage

from1%toapproximately300%,whatvalueshouldbeused?Asdesignersoftheracks,wetrytoselectanSS

valuethatprovidesthebroadestcoveragewhilekeepingoverallstructurecoststoaminimum.Forcustomersof

theselightseismicrackstheselectiongetsmoredifficultbecausetwodifferentmanufacturerIBCracksmaybe

certifiedtotwodifferentIBClevels,sothespecificationsarenotonetoone.Selectingtheracknowrequires

lookingat

the

several

parameters

and

if

different,

trying

to

determine

ifthe

rack

meets

the

specification

requirements.

OneoftheweaklinksofseveralhistoricrackdesignswhenlookingatcertifyingthemtoIBCistheendrail

bracketwhichisincapableofsupportingtheentirelateralloadsfortheIBCconditions.Abracketdesignchange

and/ortheuseoftierodassemblieshavehelpedtoresolvethisdeficiency.Typicalframeconstructioniseither

sheetsteelbentintoCchannelsorlighttubularsteelconstruction.SelectinganSSlevelof100%willyielda

designthatwilltypicallycover75%to80%ofthegeographiccontinentalUS.

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Heavy/High/SevereSeismicRacks

TraditionalUBCZone4rackswhenanalyzedtothehighestIBClevels,i.e.SSlevelsto300%,arefrequentlyfound

tobedeficientinframedesign.ThechangeinloadingparametersthatIBCimposesrequiresmorerobust

designs,especiallyforessentialandtopofbuildingcalculations.Eithernewrackshavetobedesignedorthe

existingrackshavetobecertifiedatalowermaximumSSlevel.HeaviergaugeCChannelortubularsteel

constructionfortherackframesisusedfortheseheaviestrackdesigns.Additionalbracing,modifiedseismic

restraintrailassemblies,andadditionaltierodassembliesmayberequired.Spacingbetweentherackframesis

alsoreduced

compared

to

lower

seismic

level

racks,

which

requires

additional

frames

for

certain

lengths

configurations.Alltheserequiredchangesdrivetheheavyseismicrackcostsupovertheirlowerseismic

counterpartsandeventheUBCZone4rackdesigns.

Againthechallengeformanufacturersis atwhatlevelshouldIdesignto?Doesitmakesensetocreatetwo

differentrackversionstohandlethesehigherloadstominimizecostforeach aHeavySeismicandSevere

Seismicversion?Sinceonly20%to25%ofthecontinentalUSiscoveredbytheseheavyseismicracks,

geographically,manufacturershavetoweightheadvantagesofhavingtwodifferentracklinesforthiscategory

andwhetherthecertificationcostandmanufacturingvariabilityisjustifiedforthesizeofthemarket.Thecostof

certifyingtheracksplaysanimportantroleintothisdecisionaswell,becausenowtwocertificationtestswould

nowberequired.

InfluenceofOtherCodes&StandardsWhendesigninganewrackforhighlevelIBCcompliance,addressingotherhighforcelevelcodesandstandards

isrecommended.Manyoftheforcelevelsandfrequencyspectrathatracksaresubjectedtosignificantly

overlap,especiallyiftheracksaretobecertifiedbyshaketabletesting.

IEEE693

IncludingIEEE693,theInstituteofElectricalandElectronicsEngineersstandardfortheSeismicDesignof

Substations,requirementsforthoserackconfigurationsusedbythatmarketwhendevelopingIBCrackdesigns

makessense.ThecertificationtothiscoderequiresmanyofthesameforceandaccelerationlevelsasIBCHeavy

Seismicdesignssothiscanbeincludedatminimalcosttothenewdesigncost.Theloadlevelsandfrequency

spectraof

accelerations

are

not

exactly

the

same

as

IBC,

so

an

additional

analysis

or

shake

test

needs

to

be

conductedforcertificationtoIEEE693.Theadditionalshaketablerunforthecorrectspectrawiththe

equipmentalreadyonthefixturetendstobewellworththeincrementaltestcostgiventheoverallexpenseof

theIBCshaketabletest.WhencomparingIEEE693toUBCZone4designs,changestotheframesandotherrack

componentshadtobemadetosatisfythehigherloadingrequirementsofthestandard.IfanIEEE693rackwas

alreadydevelopedforitshighseismiclevels,itislikelythatthisdesignwillmeetmanyoftheIBCHeavySeismic

rackrequirementswithlittlemodification.

OSHPD

ForthepastseveralyearsOSPHDpreapprovalhasbeenabuzzwordintheworldofrackingsystemssinceit

startedshowinguponmanyofthespecificationsforCaliforniasites.OSHPDstandsforOfficeofStatewide

HealthPlanningandDevelopmentwhichisanagencyforthestateofCaliforniathatapprovesproductsforuse

inHospitalsandotherhealthcarefacilities.HavingarackOSHPDpreapprovedassistsingettingitselectedduringabidprocessforthesefacilities.OSHPDimposesadditionalrequirementsonarackdesign,foremostit

requiresthattherackmustbecertifiedbyshaketabletestingsincealltheirfacilitiesareessentialorrisk

categoryIV.TheshaketablecertificationisactuallyarequirementimposedbyCaliforniaBuildingCode(CBC)

2010revisionwhichOSHPDreferences.

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TheadditionalitemthatOSHPDdoesimposeforloadingthatrequiresrackssatisfyingtheheaviestseismic

conditionstobemademorerobustisthattheunitundertestmustbetestedat45degreestothetwo

horizontaldirectionsinadditiontothestandardtwohorizontaldirectionsthattheothercodestestto.3

Alternatively,existingdesignscanbetestedbutmaybelimitedinapplicationiftheydonotreachthefulltest

limits.Thismaybeacceptableiftheacceptedparametermeetsufficientmarketneed,thusnotrequiringanew

design.OSHPDalsorequirestheracktobetestedwithalltheactualbatteriesthattherackistohold.Forracks

designedtoholdavarietyofdifferentbatteries,thisischallengingtohaveallthedifferentconfigurations

included.

AkeyelementinobtaininganyOSHPDpreapprovalistohavealltestingandinterfacingconductedthrougha

certifiedCaliforniaStructuralEngineer.IftestingaracksystemtoonlyIBC,havingaCASEconsultonthetest

planandbepartofthetestreportwritingandapprovalwillhelptoensurethatkeyelementsareincludedthat

willassistinanyfutureOSHPDapprovalsubmittaloftheresults.

Certification:ShakeTableTestingvs.AnalysisWithCBCandOSHPDrequiringshaketabletestcertification,manyotherAuthoritiesHavingJurisdiction(AHJs)

havestartedspecifyingthatracksinessentialfacilityinstallationbecertifiedbyshaketabletesting.These

requirementshavebeenseeninspecificationforseveralwesternUSstatesincludingWA,OR,NV,andMTwith

morespecs

being

written

with

this

requirement.

For

rack

designs

that

were

certified

by

analysis,

this

is

an

added

costforcomplianceandiseithertakenasanexceptiontothespecificationrequirement,oriftheopportunityis

sufficientinsize,thetestingisconducted.

IBC2012doesnotexplicitlystatethatshaketabletestingisrequiredforcertification,butwiththevarious

differentagencycodesreferencedbyIBC,therequirementsbecomeamatterofinterpretation.Themarket

appearstobemovingtowardsshaketablecertificationforvalidationofthedesignforessentialfacilitiesto

assurethattherackwillbestandingaftertheseismiceventasrequiredbyitsclassification.Shaketabletestingis

thebestvalidationofthedesign,buthasasignificantcostgiventhesizeandweightoflargebatteryrack

systems.Theweightandsizeofthesesystemsalsolimitstestingtoonlyafewtestlabsinthecountry.For

examplewithasystemthatAptusistesting,theentiresystemweighsover18,000lbsandis8feetlong,only3

or

4

test

table

nationally

can

handle

that

large

of

a

system

to

the

loads

necessary

for

certification.

AnchoringchangeswiththeACI31805IBC2005firstreferencedtheAmericanConcreteInstitutescodeACI31805foranchoringrequirementsfor

structures,butdidnotfullyadopttheACIrequirementuntilthe2009update.ThepreviousACI318versions

onlyrequiredthattheanchorsbestrongenoughtocarrytheloadimpartedonthem.InACI31805,thefailure

modewasconsideredintheanalysis.Abrittlefractureoftheconcrete(i.e.anchorpullout/conecracking)isno

longerpermittedinthedesign.Theconnectiontotheslabcouldnolongerbetheweaklink,theanchoror

structureconnectedtoithastobetheyieldingmembertofailure.Ifthedesignindicatesthatabrittlefacture

willoccur,thedesignispenalizedwitha0.4factortotheallowableload.Whatistheresultofthis?

1.

Newerdesignstendtohavesmalleranchorsandmoreofthem.

o Upside:Distributestheloadingoveralargerareaoftheconcreteminimizingthechanceofa

brittlefracture.

o Downside:Moreanchorholestodrill

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2. Longeranchorsrequiredifminimizinganchorholesorutilizinglargerdiameteranchors

o CommonforhistoricdesignscreatedandcertifiedtoearlierACI318versions

o Downside:Frequentlyrequires3.5to3.75inanchorsminimum.Withthedrilldepthof4inches

requiredfora3.75in.longanchor,andatypicalfloorconcretepourdepthof4inches,the

anchorsarebreakingthoughthefloors.

Breakthroughrequiresaddingplatestothefloorundersideandboltingthestructure

throughthefloor.

Alternatively,an

adapter

plate

has

to

be

created

to

change

the

bolt

pattern

and

carry

theloadwhichmayimpactcertification.

o Thisisanexampleofwherethechangeinanchoringrequirementhasledtoproblemswiththe

standardconcretefloordepth.

Theloadsimpartedontraditionallightseismicrackdesignstendnottobesevereenoughtocausesignificant

changesintheiranchoring,buttheconfigurationshavetobecheckedfortotalloadingatthesiteitisbeing

installed.

Theheavyseismicdesignstendtobethemostimpactedastheserackversionsseethehighestanchorloadsand

alargerackbeinghelddownbyonlytwolargeanchorsmaynolongermeettheanchoringrequirementsofACI

31805.

ConclusionThecertificationrequirementsforrackshavechangedwiththeretirementoftheUBCcodeandtheadoptionof

theIBCcode.Thesechangeshaveresultedinimpactstotherackdesignsespeciallyfortheheavierseismic

designs,makingthemmorerobustbutdrivinguprackcosts.Othercodesandstandardsimpactrackdesign.

IncludingcoverageforIEEE693andprovisionsforOSHPDcanhelpmaximizerackcoverageinthemarketplace.

Abalancemustbemaintainedasnosinglerackcancosteffectivelysatisfyeveryone.WiththeCBCandOSHPD

requiringshaketabletestingofessentialfacilityracks,andmoreagenciesadoptingthisrequirementinother

states,shaketabletestingofdesignsisnotonlybecomingdesired,itisbecomingarequirement.Theseareall

factorstoconsiderindevelopingnewrackdesignsorinqualifyingexistingdesignstothenewrequirements.

SpecialthanksareextendedtoBrettMcElhaneyfromMcElhaneyStructuralEngineers,LLCinReno,NVforhis

assistancewiththeIBCcodedetailsofthispaper.BrettisacertifiedCAPEandNVSE.

References1http://www.oshpd.ca.gov/fdd/PreApproval/OSHPDSpecialSeismicCertificationPreapproval.pdf2BrettMcElhaney,McElhaneyStrucuturalEngineers,LLCinReno,NV3ClaytonForbes,NTS,NEBS2012ConferencePresentationReliableMechanicalDesigns

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