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PREAMBLE(NOTPARTOFTHESTANDARD)

Inordertopromotepubliceducationandpublicsafety,equaljusticeforall,abetterinformedcitizenry,theruleoflaw,worldtradeandworldpeace,thislegaldocumentisherebymadeavailableonanoncommercialbasis,asitistherightofallhumanstoknowandspeakthelawsthatgovernthem.

ENDOFPREAMBLE(NOTPARTOFTHESTANDARD)

IS:875(Part5)1987

(Reaffirmed2008)

IndianStandardCODEOFPRACTICEFORDESIGNLOADS(OTHERTHANEARTHQUAKE)FORBUILDINGSANDSTRUCTURESPART5SPECIALLOADSANDLOADCOMBINATIONS

(SecondRevision)

SeventhReprintJANUARY2011(IncludingAmendmentNo.1)

UDC624.042:006.76

Copyright1988

BUREAUOFINDIANSTANDARDSMANAKBHAVAN,9BAHADURSHAHZAFARMARG

NEWDELHI110002

Gr5

July1988

IndianStandardCODEOFPRACTICEFORDESIGNLOADS(OTHERTHANEARTHQUAKE)FORBUILDINGS

ANDSTRUCTURES

PART5SPECIALLOADSANDLOADCOMBINATIONS

(SecondRevision)

StructuralSafetySectionalCommittee,BDC37

Chairman Representing

BrigDrL.V.Ramakrishna EngineerinChiefsBranch,ArmyHeadquarters,NewDelhi

Members

DrK.G.Bhatia BharatHeavyElectricalsLimited,CorporateResearch&DevelopmentDivision,Hyderabad

ShriM.S.Bhatia Inpersonalcapacity(A2/36,SafdarjangEnclave,NewDelhi)

ShriN.K.Bhattacharya EngineerinChiefsBranch,ArmyHeadquarters,NewDelhi

ShriS.K.Malhotra(Alternate)

iiiiiiiv



DrS.C.Chakrabarti CentralBuildingResearchInstitute(CSIR),Roorkee

ShriA.Datta(Alternate)

ChiefEngineer(NDZ)II CentralPublicWorksDepartment,NewDelhi

SuperintendingSurveyorofWorks(NDZ)II(Alternate)

DrP.Dayaratnam IndianInstituteofTechnology,Kanpur

DrA.S.R.Sai(Alternate)

DeputyMunicipalCommissioner(Engg)

MunicipalCorporationofGreaterBombay,Bombay

CityEngineer(Alternate)

Director(CMDDI) CentralWaterCommission,NewDelhi

DeputyDirector(CMDDI)(Alternate)

MajGenA.M.Goglekar InstitutionofEngineers(India),Calcutta

ProfD.N.Trikha(Alternate)

Copyright1988

BUREAUOFINDIANSTANDARDS

ThispublicationisprotectedundertheIndianCopyrightAct(XIVof1957)andreproductioninwholeorinpartbyanymeansexceptwithwrittenpermissionofthepublishershallbedeemedtobeaninfringementofcopyrightunderthesaidAct.

Members Representing

ShriA.C.Gupta NationalThermalPowerCorporationLtd,NewDelhi

ShriP.SenGupta StewartsandLloydsofIndiaLtd,Calcutta

ShriM.M.Ghosh(Alternate)

ShriG.B.Jahagirdar NationalIndustrialDevelopmentCorporationLtd,NewDelhi

JointDirectorStandards(B&S),CB MinistryofRailways

ShriS.P.Joshi TataConsultingEngineers,NewDelhi

ShriA.P.Mull(Alternate)

ShriS.R.Kulkarni M.N.Dastur&Co,Calcutta

ShriS.N.Pal(Alternate)

ShriH.N.Mishra ForestResearchInstituteandColleges,DehraDun

ShriR.K.Punhani(Alternate)

ShriT.K.D.Munshi EngineersIndiaLtd,NewDelhi

DrC.Rajkumar NationalCouncilforCement&BuildingMaterials,NewDelhi

DrM.N.KeshwaRao StructuralEngineeringResearchCentre(CSIR),Madras

ShriM.V.Dharaneepathy(Alternate)

ShriT.N.SubbaRao GammonIndiaLtd,Bombay

DrS.V.Lonkar(Alternate)

ShriP.K.Ray IndianEngineeringAssociation,Calcutta

1



ShriP.K.Mukherjee(Alternate)

ShriS.Seetharaman MinistryofSurfaceTransport(RoadsWing),NewDelhi

ShriS.P.Chakraborty(Alternate)

ShriM.C.Sharma IndianMeteorologicalDepartment,NewDelhi

ShriK.S.Srinivasan NationalBuildingsOrganization,NewDelhi

ShriA.K.Lal(Alternate)

ShriSushilKumar NationalBuildingConstructionCorporationLtd,NewDelhi

ShriG.Raman,Director(CivEngg) DirectorGeneral,BIS(ExofficioMember)

SecretaryShriB.R.Narayanappa

DeputyDirector(CivEngg),BIS

(continuedonpage18)

IndianStandardCODEOFPRACTICEFORDESIGNLOADS(OTHERTHANEARTHQUAKE)FORBUILDINGS

ANDSTRUCTURES

PART5SPECIALLOADSANDLOADCOMBINATIONS

(SecondRevision)

0.FOREWORD

0.1

ThisIndianStandard(Part5)(SecondRevision)wasadoptedbytheBureauofIndianStandardson31August1987,afterthedraftfinalizedbytheStructuralSafetySectionalCommitteehadbeenapprovedbytheCivilEngineeringDivisionCouncil.

0.2

Abuildinghastoperformmanyfunctionssatisfacorily.Amongstthesefunctionsaretheutilityofthebuildingfortheintendeduseandoccupancy,structuralsafety,firesafetyandcompliancewithhygienic,sanitation,ventilationanddaylightstandards.Thedesignofthebuildingisdependentupontheminimumrequirementsprescribedforeachoftheabovefunctions.Theminimumrequirementspertainingtothestructuralsafetyofbuildingsarebeingcoveredinthiscodebywayoflayingdownminimumdesignloadswhichhavetobeassumedfordeadloads,imposedloads,snowloadsandotherexternalloads,thestructurewouldberequiredtobear.Strictconformitytoloadingstandardsrecommendedinthiscode,itishoped,willnotonlyensurethestructuralsafetyofthebuildingswhicharebeingdesignedandconstructedinthecountryandtherebyreducethehazardstolifeandpropertycausedbyunsafestructures,butalsoeliminatethewastagecausedbyassumingunnecessarilyheavyloadings.Notwithstandingwhatisstatedregardingthestructuralsafetyofbuildings,theapplicationoftheprovisionsshouldbecarriedoutbycompetentandresponsiblestructuraldesignerwhowouldsatisfyhimselfthatthestructuredesignedinaccordancewiththiscodemeetsthedesiredperformancerequirementswhenthesameiscarriedoutaccordingtospecifications.

0.3

Thisstandardcodeofpracticewasfirstpublishedin1957fortheguidanceofcivilengineers,

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designersandarchitectsassociatedwithplanninganddesignofbuildings.Itincludedtheprovisionsforbasicdesign

loads(deadloads,liveloadswindloadsandseismicloads)tobeassumedinthedesignofbuildings.Initsfirstrevisionin1964,thewindpressureprovisionsweremodifiedonthebasisofstudiesofwindphenomenonanditseffectsonstructures,undertakenbythespecialcommitteeinconsultationwiththeIndianMeteorologicalDepartment.Inadditiontothis,newclausesonwindloadsforbutterflytypestructureswereincludedwindpressurecoefficientsforsheetedroofsbothcurvedandslopingweremodifiedseismicloadprovisionsweredeleted(separatecodehavingbeenprepared)andmetricsystemofweightsandmeasurementswasadopted.

0.3.1

Withtheincreasedadoptionofthecode,anumberofcommentswerereceivedontheprovisionsonliveloadvaluesadoptedfordifferentoccupancies.SimultaneouslyliveloadsurveyshavebeencarriedoutinAmerica,Canadaandothercountriestoarriveatrealisticliveloadsbasedonactualdeterminationofloading(movableandimmovable)indifferentoccupancies.Keepingthisinviewandotherdevelopmentsinthefieldofwindengineering,thecommitteeresponsibleforthepreparationofthestandarddecidedtopreparesecondrevisioninthefollowingfiveparts:

Part1Deadloads

Part2Imposedloads

Part3Windloads

Part4Snowloads

Part5Specialloadsandloadcombinations.

Earthquakeloadiscoveredinaseparatestandard,namelyIS:18931984*whichshouldbeconsideredalongwiththeaboveloads.

0.3.2

Thiscode(Part5)dealswithloadsandloadeffects(otherthanthosecoveredinParts1to4,andseismicloads)duetotemperaturechanges,internallygeneratingstresses(duetocreep,shrinkage,differentialsettlement,etc)inthebuildinganditscomponents,soilandhydrostaticpressure,accidentalloads,etc.Thispartalsoincludesguidance,onloadcombinations.

*Criteriaforearthquakeresistantdesignofstructures(thirdrevision).

0.4

ThecodehastakenintoaccounttheprevailingpracticesinregardtoloadingstandardsfollowedinthiscountrybythevariousmunicipalauthoritiesandhasalsotakennoteofthedevelopmentsinanumberofcountriesabroadInthepreparationofthiscode,thefollowing,nationalstandardshavebeenexamined:

a. NationalBuildingCodeofCanada(1977)SupplementNo:4.CanadianStructuralDesignManual.

b. DS4101983Codeofpracticeforloadsforthedesignofstructures.DanishStandardsInstitution.

c. NZS42031976NewZealandStandardGeneralstructuraldesignanddesignloadingforbuilding.StandardsAssociationofNewZealand.

3

4



d. ANSIA58.11982AmericanStandardBuildingcoderequirementsforminimumdesignloadsinbuildingsandotherstructures.

1.SCOPE

1.1

Thiscode(Part5)dealswithloadsandloadeffectsduetotemperaturechanges,soilandhydrostaticpressures,internallygeneratingstresses,(duetocreep,shrinkage,differentialsettlement,etc),accidentalloadsetc,tobeconsideredinthedesignofbuildingsasappropriate.Thispartalsoincludesguidanceonloadcombinations.Thenatureofloadstobeconsideredforaparticularsituationistobebasedonengineeringjudgement.

2.TEMPERATUREEFFECTS

2.1

Expansionandcontractionduetochangesintemperatureofthematerialsofastructureshallbeconsideredindesign.Provisionshallbemadeeithertorelievethestressbyprovisionofexpansion/contractionjointsinaccordancewithIS:34141968*ordesignthestructuretocarryadditionalstressesduetotemperatureeffectsasappropriatetotheproblem.

2.1.1

Thetemperaturerangevariesfordifferentregionsandunderdifferentdiurnalandseasonalconditions.TheabsolutemaximumandminimumtemperaturewhichmaybeexpectedindifferentlocalitiesinthecountryareindicatedinFig.1and2respectively.Thesefiguresmaybeusedforguidanceinassessingthemaximumvariationsoftemperature.

2.1.2

ThetemperaturesindicatedinFig.1and2aretheairtemperaturesintheshade.Therangeofvariationintemperatureofthebuildingmaterialsmaybeappreciablygreaterorlessthanthevariationofairtemperatureandisinfluencedbytheconditionofexposureandtherateatwhichthematerialscomposingthestructureabsorborradiateheat.Thisdifferenceintemperaturevariationsofthematerialandairshouldbegivendueconsideration.

2.1.3

Thestructuralanalysismusttakeintoaccount:(a)changesofthemean(throughthesection)temperatureinrelationtotheinitialtemperature(st),and(b)thetemperaturegradientthroughthesection.

*Codeofpracticefordesignandinstallationofjointsinbuildings.

5



Fig.1ChartShowingHighestMaximumTemperature

6



Fig.2ChartShowingLowestMinimumTemperature

2.1.3.1

Itshouldbeborneinmindthatthechangesofmeantemperatureinrelationtotheinitialareliabletodifferasbetweenonestructuralelementandanotherinbuildingsorstructures,asforexample,betweentheexternalwallsandtheinternalelementsofabuilding.Thedistributionoftemperaturethroughsectionofsingleleafstructuralelementsmaybeassumedlinearforthepurposeofanalysis.

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2.1.3.2

Theeffectofmeantemperaturechangest1,andt2,andthetemperaturegradientsv1andv2in

thehotandcoldseasonsforsingleleafstructuralelementsshallbeevaluatedonthebasisofanalyticalprinciples.

Note1Forportionsofthestructurebelowgroundlevel,thevariationoftemperatureisgenerallyinsignificant.However,duringtheperiodofconstructionwhentheportionsofthestructureareexposedtoweatherelements,adequateprovisionshouldbemadetoencounteradverseeffects,ifany.

Note2Ifitcanbeshownbyengineeringprinciples,orifitisknownfromexperience,thatneglectofsomeoralltheeffectsoftemperaturedonotaffectthestructuralsafetyandserviceability,theyneednotbeconsideredindesign,

3.HYDROSTATICANDSOILPRESSURE

3.1

Inthedesignofstructuresorpartsofstructuresbelowgroundlevel,suchasretainingwallsandotherwallsinbasementfloors,thepressureexertedbysoilorwaterorbothshallbedulyaccountedforonthebasisofestablishedtheories.Dueallowanceshallbemadeforpossiblesurchargefromstationaryormovingloads.Whenaportionorwholeofthesoilisbelowthefreewatersurface,thelateralearthpressureshallbeevaluatedforweightofsoildiminishedbybuoyancyandthefullhydrostaticpressure.

3.1.1

Allfoundationslabsandotherfootingssubjectedtowaterpressureshallbedesignedtoresistauniformlydistributedupliftequaltothefullhydrostaticpressure.Checkingofoverturningoffoundationundersubmergedconditionshallbedoneconsideringbuoyantweightoffoundation.

3.2

Whiledeterminingthelateralsoilpressureoncolumnlikestructuralmembers,suchaspillarswhichrestinslopingsoils,thewidthofthemembershallbetakenasfollows(seeFig.3):

ActualWidthofMember RatioofEffectiveWidthtoActualWidth

Lessthan05m 30

Beyond05mandupto1m 30to20

Beyond1m 20

Therelievingpressureofsoilinfrontofthestructuralmemberconcernedmaygenerallynotbetakenintoaccount.

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Fig.3SketchShowingEffectiveWidthOfPillarForCalculatingSoilPressure

3.3

Safeguardingofstructuresandstructuralmembersagainstoverturningandhorizontalslidingshallbeverified.Imposedloadshavingfavourableeffectshallbedisregardedforthepurpose.Dueconsiderationshallbegiventothepossibilityofsoilbeingpermanentlyortemporarilyremoved.

4.FATIGUE

4.1

GeneralFatiguecracksareusuallyinitiatedatpointsofhighstressconcentration.Thesestressconcentrationsmaybecausedbyorassociatedwithholes(suchasboltorrivetholesinsteelstructures),weldsincludingstrayorfusionsinsteelstructures,defectsinmaterials,andlocalandgeneralchangesingeometryofmembers.Thecracksusuallypropagateiftheloadingiscyclicandrepetitive.

Wherethereissuchcyclicandrepetitiveloading,suddenchangesofshapeofamemberorpartofamember,speciallyinregionsoftensilestressand/orlocalsecondarybending,shallbeavoided.Suitablestepsshallbetakentoavoidcriticalvibrationsduetowindandothercauses

4.2

Wherenecessary,permissiblestressesshallbereducedtoallowfortheeffectsoffatigue.Allowanceforfatigueshallbemadeforcombinationsofstressesduetodeadloadandimposedload.Stressesduetowindandearthquakesmaybeignoredwhenfatigueisbeingconsideredunlessotherwisespecifiedintherelevantcodesofpractice.

Eachelementofthestructureshallbedesignedforthenumberofstresscyclesofeachmagnitudetowhichitisestimatedthattheelementisliabletobesubjectedduringtheexpectedlifeofthestructure.Thenumberofcyclesofeachmagnitudeshallbeestimatedinthelightofavailabledataregardingtheprobablefrequencyofoccurrenceofeachtypeofloading.

9



NoteApartfromthegeneralobservationsmadehereinthecodeisunabletoprovideanypreciseguidanceinestimatingtheprobablisticbehaviourandresponseofstructuresofvarioustypesarisingoutofrepetitiveloadingapproachingfatigueconditionsinstructuralmembers,joints,materials,etc.

5.STRUCTURALSAFETYDURINGCONSTRUCTION

5.1

Allloadsrequiredtobecarriedbythestructuresoranypartofitduetostorageorpositioningofconstructionmaterialsanderectionequipmentincludingallloadsduetooperationofsuchequipment,shallbeconsideredaserectionloads.Properprovisionshallbemade,includingtemporarybracingstotakecareofallstressesduetoerectionloads.Thestructureasawholeandallpartsofstructureinconjunctionwiththetemporarybracingsshallbecapableofsustainingtheseerectionloadswithoutexceedingthepermissiblestressesspecifiedinrespectivecodesofpractice.Deadload,windloadandsuchpartsofimposedloadaswouldbeimposedonthestructureduringtheperiodoferectionshallbetakenasactingtogetherwitherectionloads.

6.ACCIDENTALLOADS

6.0

GeneralTheoccurrenceofaccidentalloadswithasignificantvalue,isunlikelyonagivenstructureovertheperiodoftimeunderconsideration,andalsoinmostcasesisofshortduration.Theoccurrenceofanaccidentalloadcouldinmanycasesbeexpectedtocausesevereconsequencesunlessspecialmeasuresaretaken:

Theaccidentalloadsarisingoutofhumanactionincludethefollowing:

a. Impactsandcollisions,

b. Explosions,and

c. Fire.

Characteristicoftheabovestatedloadsarethattheyarenotaconsequenceofnormaluseandthattheyareundesired,andthatextensiveeffortsaremadetoavoidthem.Asaresult,theprobabilityofoccurrenceofanaccidentalloadissmallwhereastheconsequencesmaybesevere.

Thecausesofaccidentalloadsmaybe:

a. inadequatesafetyofequipment(duetopoordesignorpoormaintenance)and

b. wrongoperation(duetoinsufficientteachingortraining,indisposition,negligenceorunfavourableexternalcircumstances).

Inmostcases,accidentalloadsonlydevelopunderacombinationofseveralunfavourableoccurrence.Inpracticalapplications,itmaybenecessarytoneglectthemostunlikelyloads.Theprobabilityofoccurrenceofaccidentalloadswhichareneglectedmaydifferfordifferentconsequencesofapossiblefailure.Adatabaseforadetailedcalculationoftheprobabilitywillseldombeavailable.

NoteDeterminationofAccidentalLoadsTypesandmagnitudeofaccidentalloadsshouldpreferablybebasedonariskanalysis.Theanalysisshouldconsiderallfactorsinfluencingthemagnitudeoftheaction,includingpreventivemeasuresforaccidental

10



situations.Generally,onlytheprincipalloadbearingsystemneedbedesignedforrelevantultimatelimitstates.

6.1ImpactsandCollisions

6.1.1

GeneralDuringanimpact,thekineticimpactenergyhastobeabsorbedbythevehiclehittingthestructureandbythestructureitself.Inanaccurateanalysis,theprobabilityofoccurrenceofanimpactwithacertainenergyandthedeformationcharacteristicsoftheobjecthittingthestructureandthestructureitselfattheactualplacemustbeconsidered.Impactenergiesfordroppedobjectsshouldbebasedontheactualloadingcapacityandliftingheight.

Commonsourcesofimpactare:

a. vehicles

b. droppedobjectsfromcranes,forklifts,etc

c. cranesoutofcontrol,cranefailuresand

d. flyingfragments.

Thecodalrequirementsregardingimpactfromvehiclesandcranesaregivenin6.1.2and6.1.3.

6.1.2

CollisionsBetweenVehiclesandStructuralElementsInroadtraffic,therequirementthatastructureshallbeabletoresistcollisionmaybeassumedtobefulfilledifitisdemonstratedthatthestructuralelementisabletostopafictitiousvehicle,asdescribedinthefollowing.Itisassumedthatthevehiclestrikesthestructuralelementatheightof12minanypossibledirectionandataspeedof10m/s(36km/h).

Thefictitiousvehicleshallbeconsideredtoconsistoftwomassesm1andm2whichduring

compressionofthevehicleproduceanimpactforceincreasinguniformlyfromzero,correspondingtotherigiditiesC1andC2.Itisassumedthatthemassm1isbreakedcompletelybeforethebrakingofmass

m2begins.

Thefollowingnumericalvaluesshouldbeused:

m1=400kg,C1=10000kNpermthevehicleiscompressed.

m2=12000kg,C2=300kNpermthevehicleiscompressed.

NoteThedescribedfictitiouscollisioncorrespondsinthecaseofanonelasticstructuralelementtoamaximumstaticforceof630kNforthemassm1and600kNfor

themassm2irrespectiveoftheelasticity.Itwill,therefore,beonthesafesidetoassume

thestaticforcetobe630kN.

Inaddition,brakingofthemassm1willresultinanimpactwave,theeffectofwhichwilldepend

toagreatextentonthekindofstructuralelementconcerned.Consequently,itwillnotalwaysbesufficienttodesignforthestaticforce.

6.1.3

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SafetyRailingsWithregardtosafetyrailingsputuptoprotectstructuresagainstcollisionduetoroadtraffic,itshouldbeshownthattherailingsareabletoresistonimpactasdescribedin6.1.2.

NoteWhenavehiclecollideswithsafetyrailings,thekineticenergyofthevehiclewillbeabsorbedinpartbythedeformationoftherailingsand,inpartbythedeformationofthevehicle.Thepartofthekineticenergywhichtherailingsshouldbeabletoabsorbwithoutbreakingdownmaybedeterminedonthebasisoftheassumedrigidityofthevehicleduringthecompression.

6.1.4

CraneImpactLoadonBufferStopThebasichorizontalloadPy(tonnes),actingalongthe

cranetrackproducedbyimpactofthecraneonthebufferstop,iscalculatedbythefollowingformula:

Py=MV2/F

where

V = speedatwhichthecraneistravellingatthemomentofimpact(assumedequaltohalfthenominalvalue)(m/s)

F = maximumshorteningofthebuffer,assumedequalto01mforlightduty,mediumdutyandheavydutycraneswithflexibleloadsuspensionandloadingcapacitynotexceeding50t,and02mineveryothercranesand

M = thereducedcranemass(t.s2/m)andisobtainedbytheformula:

where

g = accelerationduetogravity(981m/s2)

Ph = cranebridgeweight(t)

Pt = crabweight(t)

k = acoefficient,assumedequaltozeroforcraneswithflexibleloadsuspensionandequaltooneforcraneswithrigidsuspension

Q = craneloadingcapacity(t)

Lk = cranespan(m)and

l = nearnessofcrab(m).

6.2Explosions

6.2.1

GeneralExplosionsmaycauseimpulsiveloadingonastructure.Thefollowingtypesofexplosionsareparticularlyrelevant:

a. Internalgasexplosionswhichmaybecausedbyleakageofgaspiping(includingpipingoutsidetheroom),evaporationfromvolatileliquidsorunintentionalevaporationfromsurfacematerial(forexample,fire)

12



b. Internaldustexplosions

c. Boilerfailure

d. Externalgascloudexplosionsand

e. Externalexplosionsofhighexplosives(TNT,dynamite).

Thecodalrequirementregardinginternalgasexplosionsisgivenin6.2.2.

6.2.2

ExplosionEffectinClosedRoomsGasexplosionmaybecaused,forexample,byleaksingaspipes(inclusiveofpipesoutsidetheroom),evaporationfromvolatileliquidsorunintentionalevaporationofgasfromwallsheathings(forexample,causedbyfire).

Note1Theeffectofexplosionsdependsontheexplodingmedium,theconcentrationoftheexplosion,theshapeoftheroom,possibilitiesofventilationoftheexplosion,andtheductilityanddynamicpropertiesofthestructure.Inroomswithlittlepossibilityforreliefofthepressurefromtheexplosion,verylargepressuresmayoccur.

Internaloverpressurefromaninternalgasexplosioninroomsofsizescomparabletoresidentialroomsandwithventilationareasconsistingofwindowglassbreakingata

pressureof4kN/m2(34mmmachinemadeglass)maybecalculatedfromthefollowingmethod:

a. TheoverpressureisassumedtodependonafactorA/V,whereAisthetotalwindow

areainm2,Visthevolumeinm2oftheroomconsidered.

b. Theinternalpressureisassumedtoactsimultaneouslyuponallwallsandfloorsinoneclosedroom.

c. Theactionqomaybetakenasstaticaction.

Ifaccountistakenofthetimecurveofaction,thefollowing(Fig.4)schematiccorrespondencebetweenpressureandtimeisassumed,wheret1isthetimefromthestart

ofcombustionuntilmaximumpressureisreached,andt2isthetimefrommaximum

pressuretotheendofcombustion.Fort1andt2,themostunfavourablevaluesshouldbe

choseninrelationtothedynamicpropertiesofthestructures.However,thevaluesshouldbechosenwithintheintervalsasgiveninFig.5.

Note2Figure4isbasedontestswithgasexplosionsinroomcorrespondingtoordinaryresidentialflatsandshould,therefore,notbeappliedtoconsiderablydifferentconditions.Thefigurecorrespondstoanexplosioncausedbytowngasanditmighttherefore,besomewhatonthesafesideinroomswherethereisonlythepossibilityofgaseswithalowerrateofcombustion.

Thepressuremaybeappliedsolelyinoneroomorinmoreroomsatthesametime.Inthelattercase,allroomsareincorporatedinthevolumeV.Onlywindowsorothersimilarlyweakandlightweightstructuralelementsmaybetakentobeventilationareaseventhroughcertainlimitedstructuralpartsbreakatpressureslessthanqo.

Figure4isgivenpurelyasguideandprobabilityofoccurrenceofanexplosionshouldbecheckedineachcaseusingappropriatevalues.

13



6.3VerticalLoadonAirRaidShelters

6.3.1

CharacteristicValuesAsregardsbuildingsinwhichtheindividualfloorsareacteduponbya

totalcharacteristicimposedactionofupto50kN/m2,verticalactionsonairraidsheltersgenerallylocatedbelowgroundlevel,forexample,basement,etc,shouldbeconsideredtohavethefollowingcharacteristicvalues:

a) Buildingswithupto2storeys 28kN/m2

b) Buildingswith3to4storeys 34kN/m2

c) Buildingswithmorethan4storeys 41kN/m2

d) Buildingsofparticularlystableconstructionirrespectiveofthenumberofstoreys 28kN/m2

Inthecaseofbuildingswithfloorsthatareacteduponbyacharacteristicimposedactionlarger

than50kN/m2,theabovevaluesshouldbeincreasedbythedifferencebetweentheaverageimposed

actiononallstoreysabovetheoneconcernedand50kN/m2.

Note1Bystoreysitisunderstood,everyutilizablestoreyabovetheshelter.

Note2Bybuildingsofaparticularstableconstructionitisunderstood,buildingsinwhichtheloadbearingstructuresaremadefromreinforcedinsituconcrete.

Fig.4SketchShowingRelationBetweenPressureandTime

Fig.5SketchShowingTimeIntervalAndPressure

6.4Fire

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6.4.1

GeneralPossibleextraordinaryloadsduringafiremaybeconsideredasaccidentalactions.Examplesareloadsfrompeoplealongescaperoutesandloadsonanotherstructurefromstructurefailingbecauseofafire.

6.4.2

ThermalEffectDuringFireThethermaleffectduringfiremaybedeterminedfromoneofthefollowingmethods:

a. Timetemperaturecurveandtherequiredfireresistance(minutes),or

b. Energybalancemethod.

Ifthethermaleffectduringfireisdeterminedfromenergybalancemethod,thefireloadistakentobe:

q=12tb

where

q = fireaction(KJperm2floor),and

tb = requiredfireresistance(minutes)(seeIS:16421960*).

NoteThefireactionisdefinedasthetotalquantityofheatproducedbycompletecombustionofallcombustiblematerialinthefirecompartment,inclusiveofstoredgoodsandequipmenttogetherwithbuildingstructuresandbuildingmaterials.

7.OTHERLOADS

7.1

Otherloadsnotincludedinthepresentcodesuchasspecialloadsduetotechnicalprocess,moistureandshrinkageeffects,etc,shouldbetakenintoaccountwherestipulatedbybuildingdesigncodesorestablishedinaccordancewiththeperformancerequirementofthestructure.

8.LOADCOMBINATIONS

8.0

GeneralAjudiciouscombinationoftheloads(specifiedinParts1to4ofthisstandardandearthquake),keepinginviewtheprobabilityof:

a. theiractingtogether,and

b. theirdispositioninrelationtootherloadsandseverityofstressesordeformationscausedbycombinationsofthevariousloadsisnecessarytoensuretherequiredsafetyandeconomyinthedesignofastructure.

*Codeofpracticeforsafetyofbuildings(general):Materialsanddetailsofconstruction.

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8.1

LoadCombinationsKeepingtheaspectspecifiedin8.0,thevariousloadsshould,therefore,becombinedinaccordancewiththestipulationsintherelevantdesigncodes.Intheabsenceofsuchrecommendations,thefollowingloadingcombinations,whichevercombinationproducesthemostunfavourableeffectinthebuilding,foundationorstructuralmemberconcernedmaybeadopted(asageneralguidance).Itshouldalsoberecognizedinloadcombinationsthatthesimultaneousoccurrenceofmaximumvaluesofwind,earthquake,imposedandsnowloadsisnotlikely.

a. DL

b. DL+IL

c. DL+WL

d. DL+EL

e. DL+TL

f. DL+IL+WL

g. DL+IL+EL

h. DL+IL+TL

i. DL+WL+TL

j. DL+EL+TL

k. DL+IL+WL+TL

l. DL+IL+EL+TL

(DL=deadload,IL=imposedload,WL=windload,EL=earthquakeload,TL=temperatureload).

Note1Whensnowloadispresentonroofs,replaceimposedloadbysnowloadforthepurposeofaboveloadcombinations.

Note2Therelevantdesigncodesshallbefollowedforpermissiblestresseswhenthestructureisdesignedbyworkingstressmethodandforpartialsafetyfactorswhenthestructureisdesignedbylimitstatedesignmethodforeachoftheaboveloadcombinations.

Note3Wheneverimposedload(IL)iscombinedwithearthquakeload(EL),theappropriatepartofimposedloadasspecifiedinIS:1893J984*shouldbeusedbothforevaluatingearthquakeeffectandforcombinedloadeffectsusedinsuchcombination.

Note4Forthepurposeofstabilityofthestructureasawholeagainstoverturning,therestoringmomentshallbenotlessthan12timesthemaximumoverturningmomentduetodeadloadplus14timesthemaximumoverturningmomentduetoimposedloads,Incaseswheredeadloadprovidestherestoringmoment,only09timesthedeadloadshallbeconsidered.Therestoringmomentsduetoimposedloadsshallbeignored.Incaseofhighwatertable,theeffectsofbuoyancyhavetobesuitablytakenintoconsideration.

Note5Incaseofhighwatertable,thefactorofsafetyof1.2againstupliftaloneshallbeprovided.

Note6Thestructureshallhaveafactoragainstslidingofnotlessthan14underthemostadversecombinationoftheappliedloads/forces.Inthiscase,only09timesthedeadloadshallbetakenintoaccount.

Note7Wherethebearingpressureonsoilduetowindaloneislessthan25percentofthatduetodeadloadandimposedload,itmaybeneglectedindesign.Wherethis

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exceeds25percentfoundationmaybesoproportionedthatthepressureduetocombinedeffectofdeadload,imposedloadandwindloaddoesnotexceedtheallowablebearingpressurebymorethan25percent.Whenearthquakeeffectisincluded,thepermissibleincreaseisallowablebearingpressureinthesoilshallbeinaccordancewithIS:18931984*.

Reducedimposedload(IL)specifiedinPart2ofthisstandardforthedesignofsupportingstructuresshouldnotbeappliedincombinationwithearthquakeforces.

Note8Otherloadsandaccidentalloadcombinationsnotincludedshouldbedealtwithappropriately.

Note9Craneloadcombinationsarecoveredunder/Part2ofthisstandard(see6.4ofPart2ofthisstandard).

*Criteriaforearthquakeresistantdesignofstructures(fourthrevision).

(Continuedfrompage2)

PanelonLoads(OtherthanWindLoads),BDC37:P3

Convener Representing

ShriT.N.SubbaRao GammonIndiaLimited,Bombay

DrS.V.Lonkar(Alternate)

Members

ShriS.R.Kulkarni M.N.Dastur&CoLtd,Calcutta

ShriM.L.Mehta Metallurgical&EngineeringConsultants(India)Ltd,Ranchi

ShriS.K.Datta(Alternate)

ShriT.V.S.R.AppaRao StructuralEngineeringResearchCentre,CSIRCampus,Madras

ShriNageshR.Iyer(Alternate)

ShriC.N.Srinivasan C.R.NarayanaRao,Madras

SuperintendingEngineer(D) CentralPublicWorksDepartment(CentralDesignsOrganization),NewDelhi

ExecutiveEngineer(D)VII(Alternate)

DrH.C.Visvesvaraya NationalCouncilforCementandBuildingMaterials,NewDelhi

BUREAUOFINDIANSTANDARDS

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