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Fire Safety

and

Concrete Structures

Ir. J.F. Denol


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Thispublicationisavailableat:

FEBELCEM FederationofBelgianCementIndustryRueVolta8B1050Brussels

phone:003226455211fax:003226400670emailaddress:[email protected]:www.febelcem.be

Thedocumentcanbedownloadedfromwww.febelcem.be

ThispublicationexistsinFrench,DutchandEnglishversion.

TheFederationoftheBelgianCementIndustry,FEBELCEM,isgratefulforthefinancialcontributionfromtheEuropeanConcretePlatform,ECPtotheEnglishtranslationofthepublication.

Coverpicture: sourceCIMBETON

Responsibleeditor:JeanPierreJacobs,FEBELCEM

Author :JeanFranoisDenol,Structureengineer Buildings,FEBELCEM

Printedby:DeBouwkroniek

Nopartofthispublicationmaybereproduced,storedinaretrievalsystemwithoutpriorwrittenpermissionofFEBELCEM.

FEBELCEM,theauthorandthetranslators,thereviewersthatproducedthisreporthaveendeavoured to ensure the accuracy of its contents. However, the guidance andrecommendationsgivenshouldalwaysbereviewedbythoseusingthereportinthelightofthefactsoftheirparticularcaseandanyspecialistadvice.Noliabilityfornegligenceorotherwiseinrelationtothisreportanditscontentsisacceptedbytheauthor,FEBELCEM,theirservantsoragents.

FEBELCEM,2007

ISBN2960043030

ISBN9782960043037(newnomenclature)

EAN9782960043037

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Fire Safety

and

Concrete Structures

Choiceofconcrete,regulations,fireresistance,firerisk,FireSafety

Engineeringandrepairofconcreteafterfire


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Acknowledgements

Withmanythanksto,

- Professors A. Brls, J.C. Dotreppe, J.M. Franssen and J.B. Schleich of LigeUniversity,

- ProfessorsL.Taerweand P.VandeveldeofGhentUniversity,

- MessrsG.BaesandE.BriersofANPI,

- DrP.Chana(BCA),

- MrsF.Robert(CERIB),

- MrS.Horvath(CIMBETON),

- MrA.VanAcker(FEBE),

- MrT.Hietanen(FinnishAssociationofConstructionProductIndustries),

- MrP.Spehl(SECO)and

- MrU.Neck(VDZ).

JeanFranoisDenol


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7

Preamble

Thedramatic

Innovation

fire

in

Brussels

in

1967

revealed

the

absolute

necessity

for

regulations

in

the

field

of

fire

resistance

andabetterknowledgeofthebehaviourofmaterialsandstructuresinfire.

Itwasfollowed by unprecedented work in these areas. Itwas and is being carried out tomeet thepreoccupation of any

buildinguserordesigner:optimumfiresafety.

Morerecently,fireshaveoccurredinmountaintunnels,thenundertheChannelandinNewYorkon11September2001.

Firesalsooccurredevenmorerecently inMadridandatMonsonourBelgianmotorwaynetwork. Allresultedingreater

vigilance and led topeople considering the various components offires and asking questions about the behaviour of

structuresinfire.

Thispublication isaimedatconstructionprofessionals,be theyprojectdesigners,architectsorresearchoffices,authorsof

specifications,building

contractors,

insurers

or

public

authorities.

Thedocument:

- introducesthebasicconceptsusedtodiscussfireandfiresafety;

- describesthenotionoffirerisk;

- demystifiestermssuchasactiveprotectionandFireSafetyEngineering;

- putstheregulationsintocontext;

- describesthebehaviourofconcreteandsteelmaterialsduringandafterafire;

-

shows

that

concrete

integrated

into

a

structure

in

the

form

of

reinforced

concrete,

prestressed

concrete or masonry gives such structures remarkable fire resistance and good prospects forrenovationafterfire.

Itisourhopethatthisdocumentwillprovideanswerstoyourmanyquestions,aswellashelpingtoimproveunderstandingofthisextensiveandinterestingfield.

Thedocumentcanbedownloadedfromwww.febelcem.be

Itservedasreferencedocumentfordraftingbulletinnr37entitledFireprotectionbyconcreteconstructions(20pp.)whichcanalsobedownloadedfromthesamewebsite.
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Table of contents

Preamble 7

A.Introduction 11

B.Fire

safety

14

1. Purposeoffiresafety:protectionofpersonsandgoods ....................................... 14

2.Firephysics basicconcepts ......................................................................................... 16

2.1.Terminology:fireandafire................................................................................................................ 16

2.2.Thecourseofafire .................................................................................................................................. 16

2.2.1.Thefiretriangle ...................................................................................................................... 16

2.2.2.Thedevelopmentofafireflashover................................................................................ 16

2.3.NominalcurvestheISOcurve............................................................................................................ 16

2.4.Reactionandfireresistance.................................................................................................................... 17

2.4.1.Thereactiontofireofconstructionproducts Classification........................................... 18

2.4.2.ReactiontofireAttestationofconformity........................................................................ 19

2.4.3Fireresistanceofstructuralelements.................................................................................... 20

3.Regulations....................................................................................................................... 22

3.1.EuropeandirectivesandEurocodes...................................................................................................... 22

3.1.1.Europeandirectives ............................................................................................................... 22

3.1.2.TheEurocodes ........................................................................................................................ 23

3.2.StatusofBelgianfireregulations........................................................................................................... 24

3.2.1.Generalcontext....................................................................................................................... 24

3.2.2.Basicstandardsoffireandexplosionprevention ....................... ........................ ............... 24

3.2.2.1.Fieldofapplicationandreferencedate................................................................ 24

3.2.2.2.RoyalDecree(RD)of1997 ..................... ....................... ...................... ................... 25

3.2.2.3.RoyalDecree(RD)of4April2003........................................................................ 26

3.2.2.4.Theproposednewregulations.............................................................................. 26

3.2.3.Buildingpermits fireresistance.......................................................................................... 27

3.2.4.Firedetectorregulationforresidentialaccommodation................................................... 273.2.5.Oldbuildings .................... ...................... ...................... ...................... ...................... .............. 28

4.Protectionandrisks ........................................................................................................ 29

4.1.Fire:risks,factors,originandpropagation .......................................................................................... 29

4.2.Passiveandactiveprotectionandhumanbehaviour ................... ....................... ...................... ..... 29

4.2.1.Passiveprotectivemeasures compartmentalisation........................................................ 29

4.2.2.Activeprotectivemeasures................................................................................................... 31

4.2.3.Humanbehaviour ...................... ...................... ...................... ....................... ...................... ... 33


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5.Thermalmechanisms ..................................................................................................... 36

5.1.Heattransfermechanisms...................................................................................................................... 36

5.2.Mainfactorsaffectingthetemperatureofgases.................................................................................. 36

5.2.1.Thefireloadandrateofheatrelease(RHR)....................................................................... 36

5.2.2.Ventilation............................................................................................................................... 38

5.2.3.Thermalcharacteristicsofwalls .................... ....................... ....................... ...................... ... 38

5.3.Fireseverity.............................................................................................................................................. 39

6.Actions............................................................................................................................... 40

6.1.Mechanicalactions................................................................................................................................... 40

6.2.Thedifferentmodelsforthermalactions ............................................................................................. 40

6.2.1.Nominalcurves....................................................................................................................... 40

6.2.2.Parametriccurves................................................................................................................... 40

6.2.3.Zonemodels............................................................................................................................ 41

6.2.3.1.Singlezonemodels................................................................................................. 41

6.2.3.2.Twozonemodels.................................................................................................... 41

6.2.4.Localisedfiremodels ...................... ...................... ...................... ...................... ..................... 41

6.2.5.CFD(ComputationalFluidDynamics)models.................................................................. 41

6.2.6.Whichcurve,whatmodel?.................................................................................................... 41

7.Materials ........................................................................................................................... 43

7.1. Physicalandchemicalphenomenainconcrete ................... ...................... ...................... ................... 43

7.2.Themechanicalandthermalcharacteristicsofconcreteandsteel.................................................... 45

7.2.1.Normalconcrete ...................... ...................... ...................... ...................... ...................... ....... 45

7.2.2.Lightconcretes........................................................................................................................ 47

7.2.3.Highstrengthconcretes ........................................................................................................ 47

7.2.4.Selfcompactingconcretes..................................................................................................... 48

7.2.5.Steel ..................... ...................... ...................... ...................... ...................... .................... ......... 48

7.2.6.Comparisonofthemechanicalcharacteristicsofsteelandconcrete............................... 50

8.Protectionandriskcalculations ................................................................................... 51

8.1.Verificationoffireresistance:calculation............................................................................................. 51

8.1.1.Threemethods,threelevels .................................................................................................. 51

8.1.2.Tabulatedvaluesmethod(level1)....................................................................................... 52

8.1.2.1.Fieldofapplication .................... ...................... ...................... ...................... ........... 52

8.1.2.2.Readingthetables................................................................................................... 52

8.1.2.3.Axisdistance............................................................................................................ 53

8.1.2.4.Isostaticgirders ....................................................................................................... 54

8.1.2.5.Continuousgirders................................................................................................. 55

8.1.2.6.Slabs.......................................................................................................................... 55

8.1.2.7.Columns..................... ...................... ...................... ...................... ...................... ...... 55

8.1.2.8.Walls ...................... ...................... ...................... ...................... ...................... ........... 56


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8.2.FireSafetyEngineering........................................................................................................................... 56

8.3.Firerisk ..................................................................................................................................................... 62

8.3.1.Performanceandprescriptiveregulations.......................................................................... 62

8.3.2.Methodsofassessingfirerisk............................................................................................... 62

8.3.2.1.Qualitativemethods ..................... ....................... ....................... ...................... ...... 62

8.3.2.2.Semiquantitativemethods.................................................................................... 62

8.3.2.3.

Quantitative

methods............................................................................................. 638.4.Industrialbuildings................... ...................... ...................... ...................... ...................... ..................... . 64

8.4.1.Classificationofactivitiesandfirerisksforindustrialbuildings............................. ........ 64

8.4.2.Warehousefires...................................................................................................................... 65

8.5.Tunnels...................................................................................................................................................... 71

C. Examplesofthefirebehaviourofconcretestructuresduring

fireincidents 73

1.Instructivefires............................................................................................................ 73

1.1.WhathappenedinMadrid? ................................................................................................................... 731.2.TheTroisFontainesviaduct .................... ...................... ...................... ...................... ...................... ....... 75

2.Buildingdesign ............................................................................................................... 76

3.Firetestsforbuildings ................................................................................................... 77

3.1.Ghent1974................................................................................................................................................ 77

3.2.Cardington2001....................................................................................................................................... 78

D.Repairofconcretestructures 79

1.Inspectionmethods......................................................................................................... 79

1.1.Visualobservations ................................................................................................................................. 79

1.2.Testmethods .................... ...................... ...................... ...................... ...................... ................... ............. 79

2.Repairoptions.................................................................................................................. 79

E.Appendix 81

Appendix1 Discussiononsprinklersystems ............................................................. 81

F.Bibliography 85

1.Generalbibliography ..................................................................................................... 85

2.Standards .......................................................................................................................... 87

3.Regulations....................................................................................................................... 87


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A. IntroductionThetragicfire[1]atInnovationinBrusselsin1967costthelivesof more than 250 people. Hindsight shows that this had tohappensoonerorlater.Incaseoffire,severalpublicbuildingsoftheperiodwouldbetransformedintodeathtraps.

AtInno,forexample,therewasnofiredetectionsystemandnosprinklers; no compartmentalisation; no emergency exits; themetallic structure was not protected, highly inflammablecardboard panels covered the walls and were used as falseceilings; the fire services access to the flamingbuilding wasseverely hamperedby the advertising hoardings thatblockedthewindowson thefaadeandby thenarrownessof thestreetcongestedbyheavytrafficandmanyparkedcars.

The shock causedby the catastrophe forced the authorities totakeaction.Veryquickly,theMinistryoftheInteriorfinaliseda

series of laws, royal decrees and ministerial circulars, and theBelgian Institute for Standardisation (IBN) in turn publishedstandards.

Belgiumscasewasnotunique;allotherEuropeancountrieshad

to face up to the same problem. Just about anywhere,laboratories were hastily established and series of testsundertaken.

In 1988, the Construction Products Directive issuedby theCounciloftheEuropeanCommunitiesrecognisedfiresafetyasoneofthesixessentialrequirementswhichconstructionsworksmustsatisfy.

Today,afterdozensof years ofgestation,genuineharmonisedEuropean product standards are finally appearing, alongwith European calculation standards. These are intended toserveasabasisfornationalregulations.

Evenifconcreteremainsthematerialparexcellencewhichhasthebestfireresistance,wefeltitwasvitaltofirstvisitorrevisitthebasics of the physics of fire. In the highly emotional wayfiresareperceived,thisshouldprovideelementsforassessmentand improveourunderstandingof thebehaviourofstructuresinfire.

It is vital thatbuildings and structures are designed andbuiltwhich protect both persons and goods thoroughly andeffectively. The annual statistics for deaths causedby fires inhomesandelsewherebringusbacktotheharsh,sadreality.Atthe same time, these events allow us to gather information on

firesafetyforthedesignofconstructions.An impressivebody of national and international legislationexists to protectus from therisksof fire.Itis constantlybeingupdated. Relevant and introductory information should beavailable for construction professionals, be they projectdesigners, architects or research offices, authors ofspecifications, entrepreneurs, insurers or public authorities.Thispublicationisaimedspecificallyatthesepeople,whoneeda summary of the importance of fire safety in the design of

buildings and theroleconcrete canplay in that. This summarycoversbuildingsandstructures.Referenceismadetothetunnelsandotherextremeconfigurationsinwhichconcreteisused.

Nomoredisastrousfires

WecanreadontheplansfortheHennebiquebridge(Paris,24November1904)builtinLigein1905.Thisinspired

designer,inventorofthestirrupsforreinforcedconcrete,hadquicklyunderstoodtheextraordinaryappealofthismaterial.

Heturneditintohisadvertisingslogan.

Afterthefire,allthatremainedofInnovationwasapileoftwistedsteel


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Why choose a concrete structure?

Concrete is specified inbuildings and civilengineering projects for several reasons: questions of cost, of speed of construction, ofaestheticorarchitecturalappearance.Nevertheless,oneofthekeyinherentbenefitsofconcreteisitsperformanceinfireatnoextracost,anaspectwhichcanprovedecisiveinrelationtothefactorsaffectingthedecisionmakingprocesswhendesigningaproject.

Concrete[21]andconcretestructurespresentparticularlyfavourablecharacteristics:

- Alongwithmasonry,concreteistheonlyloadbearingmaterialcapableofremarkableresistancetofire,withnoadditionalprotectivemeasureofanykindwhatsoever,suchasacoatingofplasterorintumescentpaint.Itspropertiesinrelationtoitsbehaviour in fire do not alter over time. They remain permanent, withno additionalmaintenance costs. Simply choosingconcreteconstitutesasignificantelementinthepreventivesafetymeasuresagainstfire;

- Concreteofferstherequiredresistanceinaneconomicway:moreoftenthannotallthatisrequiredistoverifytheconcretecoverandtheminimumdimensionsgiveninthecalculationstandardstables.ThissimpletablebasedapproachavoidstheneedtogetembroiledinthecomplexartofFireSafetyEngineering;

- Concrete loadbearing structures offer extremely high resistance in fire. For example, in large, multistoreybuildings, itreducesrisksfortheoccupantsofthistypeofbuildingandforthefirefightingservices.Thesecanenterthebuildingandtakeactionatclosequartersandthereforeeffectively;

- Thankstotheirthermalinertiaandmassivity,concreteelements,incontrasttounprotectedmetalsections,withstandhigh

temperaturesforaverylongtime,withaminimumofdeformation.Reinforcedconcreteslabreinforcementsonlyreachtheircriticaltemperatureof500Cafter2hours,atadepthof3,5cm.Alightweightaggregateconcretecansatisfyevengreaterdemands.Itconstitutesaneffectivebarrieragainstthespreadoffire;

- Thehighthermalinertiaofconcretewallsisalsoofconsiderableinteresttodelayingflashover;

- Concreteisnotcombustible:inafire,noelementdetachesitselffromitordripsfromit.Itdoesnotmelt.Concretedoesnotpropagatefireanddoesnotgiveoffsmokeortoxicgases,eveninthemostextremetemperatureconditions;

- Concrete fire walls perfectly combine fire resistance, sound insulation and thermal inertia. The effectivecompartmentalisationoflargespacesusingconcretefloorsandwallsreducestheriskoftotal lossasaresultoffire.Theseelementstogetherwithconcretestairwellsprovidesafe,simpleandeconomicescaperoutes;

- Thanks to their intrinsic safety in fire, concrete constructions provide greater architectural freedom. Fire demands weighheavilyonothermaterialsthathavetobeprotectedbycoveringsorrequireactiveprotectivemeasuresthatdonotapplytoconcrete.Inthiswaythearchitectcanconcentratefullyonhisarchitecturalcreation;

- Concretestructural elementsgenerallyhave reservesofprotectionagainst fire that canbeusedatnoextracost if the fireprotectionrequirementsaretightenedup,notablyifthebuildingisreconverted,asisoftenthecase;

- Concretes excellent properties in fire are valuedby property insurers: concretebuildingsbenefit from the cheapest fireinsurancepremiums;

- Concreteisnotafraidofwater,whichisoftenusedinlargequantitiestoputoutfires;

- Thanks to its use in the compartmentalisation of spaces, concrete prevents fires from spreading, thereby reducing theassociatedenvironmentalimpact.Concretedoesnotgenerateanytoxicresidueswhenattackedbyfire;

- Becauseoftheprotectionitoffers,concreteallowsactivitiestocontinueininstallationsofvitalimportance.Italsoprotects

thecompartmentsthathouseourcultural

heritage;- Theuseofprefabricatedconcreteelementsallowsspeedofexecution,whichisgreatlyappreciated;

- Concretefloorsaresubjecttolittledeformationcomparedwithothermaterials;

- Afterafire,concretealsoofferssimplerestructuringatlittlecost.


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The reader will note that this document does not constitute acompleteguidetofiresafety.Rather,itisageneralviewofthekey aspects of fire safety and the behaviour of concrete inconstructions.ThisdocumentisthereforeagoodintroductiontoEurocodes1and2firepart.

Alistofthevariouspublications,standardsandsitesisprovidedattheendofthedocumentforallthosewhomightrequiremore

detailed

technical

information.

The reader looking for A short but relevant document! willbenefit from the above introduction and the texts in the ochreboxes, such as that on the use of concrete faades in industrialbuildings(seep69)orconcreteroadwaysintunnels(seep71).Hewill note the examples of the fire behaviour of concretestructuresinfire.Theseexamplescanbefoundattheendofthedocument(seep73).

Regulations(seep22)arethesubjectofachapterwhichmaybereadindependently.InthechapterdevotedtotheRoyalDecreeof 1997 (see p25), everyone can profit from abrief reminder oftheprovisionsimposedbyBelgianregulationsonstairwells,liftshafts,

aprons

and

piers.


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B. Fire safety

1. Purpose of fire safety:protection of persons and

goodsThe purpose of fire safety [18], [20] is the effective protectionagainsttherisksoffireofpersonsandgoods.Morespecifically,thisconcerns

- Savingthelivesoftheoccupantsofthebuilding- Protectingthelivesoftheemergencyservices- Protectingtheintegrityofthebuilding- Savingadjacentbuildings

Intheabsenceofaspecificinsurancepolicycoveringproductionstoppages,inindustrialbuildings,insurancepremiumsadjusted

according to the risks run only cover loss of goods, and notproductionstoppages.Thisbecomesextremelyimportantwhenyouconsiderthatalmost50%ofbusinessthatsufferamajorfiregobankrupt[6].

Thebasicrequirementsoffiresafetyconsistin

- reducingthedevelopmentofthefire;- avoidingspreadoffire;- ensuringthespeedyevacuationofoccupantsinrelative

safety;- facilitatingtheinterventionofthefireservice.

The following table [33] shows how concrete elements satisfythesebasicrequirementsoffiresafety.

Fire safety [32] cannotbe absolute. It consists of reducing therisksby taking a series of measures. Each of these measures isinsufficientinitself,butahighdegreeofsafetycanbeachievedbycombiningthem.

InmanyEuropeancountries, there isa tendency [33] toreducetherequirementsplacedonthefireprotectionofbuildings.Thisdirectly affects the resistance to fire required of structuralelements.Themainreasonforthisattitudestemsfromthebelief

thatonlytheresistancetofirenecessarytoprotectpersonsneedbe regulated by the public authorities. Responsibility forprotectingbuildings and goods is therefore transferred to thegeneral public. In its annual report for 1999, the World FireStatistics Centre presented an international comparison of thecosts associated with fires. This comparison reveals theimportanceoffireprotection:

- Thetotalcostoffiredamageisbetween0,2and0,3%ofgrossnationalproduct;

- Thenumberofdeathscausedbyfiresvariesper100000inhabitantsfrom0,55inSwitzerlandto1,32inBelgium

and2,12inFinland.

- The sum of the costs associated with protectivemeasures and fire damage amounts to 0,6% of grossnationalproductonaverage.

basicrequirementsoffireprotection

reducethedevelopmentofthefire

avoidthespreadofthefire ensurethespeedyevacuationofoccupantsinrelativesafety.

facilitatetheinterventionofthefireservice

preventiveandprotectivemeasures

e.g.Usingnoncombustiblewalls,floorsandceilings

e.g.Usinghighlyeffectivefirewallsbothinternallyandexternally

e.g.Escaperoutesconsistingofhighlyfireresistantelementsthatcanbeusedforlongperiods

e.g.Highlyfireresistantloadbearingstructuresthatallowthefiretobetackledeffectivelywithinthebuilding

Relationshipsbetweenbasicfireprotectionrequirementsandprotectivemeasures


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These figures show the need for general fire protection.Reducing thenumberofdeathsby fireandthecostsassociatedwithfiredamageshouldbeundertakenasanindisputablesocialandeconomicaim.

Limiting pollution caused by smoke, toxic gases andcontaminatedfirefightingwatershouldinturnhelpprotecttheenvironment.

Theoveralleffectsoffireprotectioninvolvingtheuseofconcrete

elements(Neck,2002)

The reports of the NFPA [41] (National Fire ProtectionAssociation) state that in the United Statesbetween 1977 and2002, the average financial loss per fire affecting the structureroseby 51%. This increase is linked to a relaxing of the safetyrequirements specifically for the protection ofbuildings. Thesedirectorindirectlosses,suchastherelocationofresidentsortheactivities of the company, can have an enormous economicimpact on the community. Regulations should take this impactintoconsideration.

Tofightfireeffectively,thefirefightingservicesmustbeabletooperate inside the building [23]. In this respect, concretestructures are the most reassuringboth at the evacuation stageandthefirefightingstage.

Accordingtoobservations[32]madeinEnglandof840fires,theprobabilityofthestructurebeingdestroyedislow(1%)(takingallstructuralmaterialstogether!),whilethelocaliseddestructionofastructuralelementisgreater(15%).Thisgivesanideaoftheimportanceofbeingabletorepairstructures.

The concrete sector is involved inefforts to optimise the safetyand economy of projects. The presentation in this document ofthe scientific approach used by Fire Safety Engineering isworth risking opening. It thus hopes to provide an objectiveview of the problem. Most certainly it will reject simplistic orcompartmentalised and nonintegrated approaches. Theinterests of the parties concerned: owners, architects,buildingcontractors, product manufacturers, insurers, occupants of

buildings and visitors, do not necessarily converge. Balancedregulations should provide for the training and acceptance ofpeopleforcalculationsandinspections.

A lack of measures and means on the part of the public

authoritiesshouldbeaclearindicationthatreliablesolutions

should be favoured, and responsibilities assigned to those

withboththewillandthecapabilitytotakethemon.


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2. Fire physics - basic concepts

2.1. Terminology: fire and a fire

Fire involves combustion [4]. This is found in furnaces andboilers in theformof controlledcombustion.Afireinvolvesuncontrolledcombustion.Itthenassumessuchasizethatitcan

causeafire.

There is a fundamental differencebetween fire and a fire. Fireexperts master a controlled combustion which corresponds tothe scenario definedby a predetermined thermal programme.Thesearefoundintheglassindustry,theceramicsindustryandother industries,aswellas in test laboratories,allplaceswherefiresareproducedinfurnacesortestchambers,wheresmokeischannelledsoasnottoinconvenienceoperators.Thefireexpertsthatarefiremeninturnhavetotryandmasteranuncontrolledcombustion which corresponds to a scenario strewn withunforeseenaspects,withhumanlivesthathavetobesaved,whoalsohavetosave,intervene,andsoon.

2.2. The course of a fire

2.2.1. The fire triangle

For a fire to start [5], three elements must be presentsimultaneously: oxygen (21% volume in air), combustiblematerialsandaheatsource.Thesemakeupwhatitisconvenienttocallthefiretriangle,showninthefigurebelow.Thefirsttwoelements [19] combust when the inflammation temperature isreached. The combustion of carbon produces carbon dioxide

CO2

and,

if

there

is

a

lack

of

oxygen,

it

produces

the

well

known

gasCO,whichishighlydangeroustoman.

2.2.2. The development of a fire flash-over

A fire involves a development phase in which the temperatureincreases,thenadeclinephaseinwhichthistemperaturedrops.

Aheatsourcecausesafiretostartinaquantityofmaterials.Thefirst gases and smoke appear. In a closed environment, undertheactionoftheincreasingheat,thesmokerisestotheceilingin

a

plume.

At

this

point,

it

spreads

radially

along

the

ceiling

until

itreachesawallandcontinuesdownwardswhereitstagnatesinanupperlayerbeneaththeceiling.

In general, the room contains a cool lower layer composed ofambient air, gas and a warm upper layer (twozone model). Atemperature in the order of 200 C causes windows tobreak,creating asudden influx of freshoxygenwhich gives the fire anew lease of life. The upper layer moves closer to the floorbecauseitincreasesinvolumeasaresultofbeingfedbyplumesofsmoke.

Duringthedevelopmentofafiretheremaybeatimewhenthetemperatureofthegaseousmixtureoftheupperlayerissohighthat it causes any combustible element in the compartment toignite. This phenomenon is known as flashover. It generallycorresponds to a temperature of 500 to 600 C. The extremelyrapidrisein temperatures inthecompartmentand the increaseinthereleaseofheatcausethesmoketobestirredupwherethelayersmix(singlezonemodel). Thefireisthensaidtobefullydeveloped.

Thesedifferentphasesinthedevelopmentofafirearedepictedinthenextgraphic,showingtheevolutionofthetemperaturein

thecompartmentasafunctionoftime.Thefirewillbecontrolledbythefuelifthereissufficientoxygenavailable for combustion. It willbe controlledbyventilation ifthereisinsufficientoxygen.

The fire resistance of columns,beams, walls and slabs mustpreventthespreadofthefireandthecollapseofthestructuretoallowtheextinguishingoperationstopassoffsmoothlywithoutthefiremenbeingexposedtoexcessiverisks.

When more or less 70% of the fuel hasbeen consumed, thetemperatureofthegasdrops.Forinformation,thecarbonisationspeedofwoodisbetween3and6cmanhourdependingonits

species.

2.3. Nominal curves the ISO curve

Thesimplestwayofrepresentingafireistousenominalcurvesgivingtheevolutionofthetemperatureofthegasesasafunctionoftime.

Historically, nominal curves were developed to test structuralelements experimentally with a view to establishing a relativeclassification forboth their resistance and reaction to fire (see2.4below).Itishighlydesirableforelementstestedindifferent

furnacesto

be

subjected

to

the

same

thermal

action.

In

terms

of

modelling a fire in a building, these curves constitute aconventionalreference.

For reasons of history and simplicity, they remainby far themost common method of representing a fire in practicalapplications.

The notion [32] of time of resistance conforms to theperformancebasedconcept:notypeofmaterialisexcludedandtheperformanceoftheelementisprescribed.

Thecurvesmostfrequentlyusedareshowninthefigurebelow.Theywereproduced fromexperienceofrealfires,belonging to

Heat source

Combustible

material

Oxygen

igure:thefiretriangle


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one of the three main categories, namely buildings,petrochemicals/oilrigsandtunnels.

0

200

400

600

800

1000

1200

1400

0 30 60 90 120 150

Time (minutes)

Temperature(C)

Increased hydrocarbons curve

(tunnels)

Hydrocarbons curve(petrochemicals and oil rigs)

ISO 834 curve (buildings)

Figure:Differenttemperaturecurves

ThestandardISOcurve:g=20+345log10(8t+1)

Where g=temperatureofgasesinthecompartmentinC

t=timeinminutes

For the ISO curve it is easy to remember that, after hr., theambient temperature reaches around 745 C and continues toincreasebyaround100Ceachtimethetimeisdoubled.

Inthisequation,the twophases[5]thatoccurduringafirecan

easilybeidentified:theflashoverperiodinwhichthereisaveryrapidincreaseintemperaturetoaround800C,thentheperiodwhenthefireisfullydeveloped.

The hydrocarbons curve [55] developed in the 1970sby thepetrol company Mobil shows a very rapid increase intemperaturewithatemperatureof900Cinthefirst5minutesand a plateau at 1100 C. This research wasbegun to perfect atest procedure to evaluate fire protection materials for oil rigsandpetrolcomplexes.

More severe hydrocarbon curves have been perfected morerecently following the wave of major fires in tunnels, which

revealed that more severe fire scenarios had tobe considered.

The Netherlands have perfected the RWS curve, simulatingthe behaviour in fire of tankers transporting petrol with acalorificpowerof300MW,generatingatemperatureof1350Candcausingafirethatlasts2hours. TheNetherlandsdevelopedthis curve as a realistic and essential thermal calculationreference to guarantee thebehaviour of their tunnels passingbeneaththeirhydraulicworks.

The Germans have developed their curve: the RABT curve

(sometimesknownastheZTV),lessseverethantheRWScurve,rising to 1200 C for 1/2 hour before falling linearly to theambienttemperatureafter170min.

Anewcurve,differentfromtheRWSandRABTcurves,knownby thenameincreasedhydrocarbonscurve (IHC),has finallybeencreatedbyincreasingthehydrocarbonscurveby18%.Thetemperatureplateauistherefore1300C.

ConcreteelementscaneasilywithstandanISOfireof1hour. Agreaterresistancecaneasilybeobtained,which isanythingbutthe case with unprotected metal elements. After 10 to15minutes, steel reaches 500 to 600 degrees and its resistancedeclinesrapidly. Boardsandpaintsareavailablewhichinsulatesteel,butpoorsiteexecutionandreporteddegradationofthesematerialscanhavedramaticconsequences.

2.4. Reaction and fire resistance

Reaction to fire [18] applies to construction materials. Itmeasuresallthepropertiesofconstructionmaterials inrelationto thebirth and development of a fire. It is characterisedbycalorific potential [5], noncombustibility, inflammability, themeans of propagation of flames on the surface of materials,

where applicableby other properties such as the formation ofsmokeandtheproductionoftoxicgases.

Development (ignitionand propagation)

1100 C

Full intensity Decline(extinction)

Controlled byventilation

Contrlled bythe fuel

Controlledby the fuel

Temperature

Time

Reaction to fire Resistance to fire

Flash-over

Figure:phasesinthedevelopmentofafire


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18

Resistancetofireappliestostructuralelements.Itisameasureof their ability to perform the role assigned them despite theactionofafire.

These two notions are therefore completely different. The firstconcernsthebirthanddevelopmentofthefire,whilethesecondoccursinthefullintensityphase.Neitherareacanbeneglectedin fire prevention. The instructions therefore include

requirementsrelatingtobothaspects.

Thus, wood [5] is a material that does not react well to fire woodburnswhilewoodenbeamsandcolumnsarestructuralelementswithasignificantresistancetofire.

Conversely,steelisamaterialwithagoodreactiontofire,whilesteel elements are structural elements with a very poorresistancetofire.

Finally, concrete combines the two qualities. This is why it isthepreferredmaterialforstructuralelementswheregoodfirebehaviourissought.

Becausetheyaremorepermanent,thechoicesthatimprovethefire resistance of structural elements offer greater safety forpreventingfires.Eachmodification(renovation,enlargement)issubject to a newbuilding permit or a revision of the operatinglicencewherethefireservicesareconsulted.

The same is not true of finishes, especially in residentialbuildings,wheretheowner/tenantof thepropertycanalterthecontentof thebuilding and the nature of the claddings tosuchan extent that the load and risk of fire are fundamentallychanged.

2.4.1. The reaction to fire of constructionproducts - Classification

WithregardtothereactiontofirementionedinCEmarks,everyconstructionprofessionalowesittohimselftogettogripswithaminimum of European language to understand the new testsandclassificationstandards.

Thissystemofclassification[40]wasthesubjectofdecisionsbythe European Commission on 08022000 [61], [63] and26082003. As the decrees implementing this marking appear,manufacturershavetocheckthattheirproductscomplywiththenew European requirements and if necessary modify theseproducts.

The number of classes, the logic which enabled theirconstruction and some of the tests used differ from currentBelgian practice, so much so that there is no correspondencebetween current Belgian classification and the system ofEuroclasses.

Constructionproductsareseparatedintotwomainfamilies[12]:that of floor coverings and that of other products. Thisdistinctionisexplainedbythefactthatthescenariosofexposuretofireandthebehaviourofthematerialsdifferinbothcases.Ineach of these groups, the Euroclasses, which number seven,

definedinNBNEN135011:2002[105],areasfollows:

A1Fl, A2Fl, BFl, CFl, DFl, EFl, and FFl for floor coverings (Fl

forfloor) A1,A2,B,C,D,E,andFforotherconstructionproducts.

ClassesA1andA2(orA1Fl,A2Fl)areassignedtoproductswitha

low or very low organic fraction which are therefore hardly ornotverycombustible.

ClassesBtoE (orBFl,EFl)areassignedtocombustibleproducts

whichcontributesignificantlytofiredevelopment,forbothfloorcoverings and other products. Class E applies to products thatmeet the minimum German marketing criterion and class Fapplies to unclassified products or those that have failed theleastseveretest.

Alongside the reaction itself, some construction products aregiventwoadditionalqualifications:

s1, s2 or s3 for the productionofsmoke (s = smoke: thehigherthenumber,themoresmokeisemitted):

s3:nolimitforsmokeemission;

s2: the total emission of smoke and the speed of

emissionarelimited;

s1:stricterrequirementsthanfors2.

d0,d1ord2forbehaviourfacedwithfallingdropletsandburningparticles: (d = drop: the higher the number, themoredropsareproduced):

d2:nolimit;

d1:productionofdroplets/incandescentparticlesoveraspecificperiod;

d0: no production of droplets / incandescentparticles

The table [51] below allows reaction to fire classes to betransposedbetween the old French classification and the newEuropeanclassification(EN135011):

ClassestoNFEN135011newclassification

Requirementofoldclassification

A1 IncombustibleA2 s1 d0 M0A2 s1 d1

s2 d0A2

s3 d1s1 d0s2 d1Bs3

M1

s1 d0s2 d1Cs3

M2

s1 d0 M3s2 d1Ds3

M4(nondripping)

AllclassesotherthanEd2andF

M4

In1996,theEuropeanCommissionpublishedaregulatorylistof

constructionmaterials[34],[61]whichmaybegroupedtogether


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into protection class A1 without further examination. This listcontains the different types of concrete or mineral constituentsusedinconcrete.Forthematerialsonthislist,thisclassificationis linked to the requirement of a level of organic constituentsevenlydistributedoflessthan1%.

Concrete, a mineral construction material [33], satisfies therequirements of class A1because in fact it is not inflammable

anddoesnotcatchfireatthetemperaturesencounteredinfires.Noburningelementisreleasedbyorrunsoffconcrete.

According to this system, construction materialsbelonging toclass A2 are not considered inflammablebut typically containinflammable constituents which could thereforeburn in a fireandcausedamage.

The behaviour in fire of a product largely depends on thethermal stress scenario to which it is subject. To reproduce thefire scenarios most frequently encountered inbuildings, threelevels of thermal exposure are envisaged. These correspond tothreestagesofpossibledevelopmentofafire:

attackbyasmallflame; attackby a fully developed fire in the adjacent room or

byaburningobject; attackbyafullydevelopedfireintheroom.

The Euroclasses are subject to 5 types of test, on samples, 4 ofwhicharenew,notablytheSBI(singleburningitem).

2.4.2. Reaction to fire Attestation ofconformity

Thetable[64]belowexplainsthedifferentlevelsofattestationof

conformity required, depending on the products and theirclasses. These attestation systems allow the presumption ofconformitywithproductstandards tobeobtained inrelationtothefiresafetystake.

Class systemsofattestationofconformity

A1*,A2*,B*,C* 1A1**,A2**,B**,C**,D,E 3

(A1toE)*** 4* productsundergoingatreatmenttoimprovetheirreactionto

fire** productswithouttreatment

*** productsdeemedtosatisfy,classifiedwithouttest

Thetablebelowdetailsthetasksdedicatedtoeachpartyforthedifferentlevelsofattestationofconformity:

SystemsTasksdedicatedtoapprovedbodies

Tasksdedicatedtoproducer

1 initialtypetests initialinspectionofthe

factory

productioncontrol supplementarytests

3 initialtypetestsbytheapprovedlaboratory

productioncontrol

4 initialtypetests productioncontrol


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2.4.3 Fire resistance of structural elements

The ability of a concrete construction to retain its loadbearingfunctionfortherequireddurationisexpressedasfollows:

Ed,fi(t)Rd,fi(t)

where: Ed,fi(t) is the calculated value of the effect of actions,loadsatthetime(t)ofthefire;

Rd,fi(t) is the calculated value of the constructionsresistancetohightemperaturesattime(t).

The fire resistance of structural elements is measured in testsunder the thermal stress described by the ISO curve. Itcomprises the three criteria that apply to most constructionelements:

- stabilityR(loadbearingcapability);- flameintegrityE;- thermalinsulationI.

In some Member States, the performance requirement W(limited radiation) may be required. To this are added

supplementary criteria: M (impact resistance), C (automaticclosure) and S (smoke integrity) as well as suffixes providingspecific details relating to the configuration of exposure to thefireandthefieldofapplicationofthetestresults.

The degree of resistance REI of the element is the timeimmediately below the observed duration, chosen from thevalues15,20,30,45,60,90,120,180,240,360minutes,[61],[62].

By way of example, a test on a loadbearing wall gives thefollowingresults:

Time ClassificationLoadbearingcapacity 130min R120

Fireintegrity 92min RE90Thermalinsulation 46min REI45

ThewallthereforeenjoysclassificationsR120/RE90/REI45

The stability criterion (R) of an element indicates the timeduringwhichitsmechanicalresistanceisguaranteedunderthestatic load defined in 6.1 and during which its deformationsremain compatible with its function in the stability of theconstruction(generally1/30thof itsspan).ItcorrespondstotheFrenchdenominationofStableauFeuSF.

The criterion of flame integrity (E) is no longer satisfied

when a cotton cloth, placed at a distance of 2 to 3 cm from anopening,spontaneouslycombusts.

TheFrenchdenominationPareFlammePFcorrespondstotheRE.criteria.

The criterion of thermal insulation (I) is satisfied if theincreaseintemperatureoftheunexposedsurfaceoftheelementremainsbelow140Conaverageand180Coccasionally.

The French denomination CoupeFeu CF corresponds to theREIcriteria.

These last two criteria enable inflammation of materials incontactwiththisfacetobeavoided.

In loadbearing structural elements such as beams, columns,walls and slabs, the resistance R prevents the structure fromcollapsing. Ingeneral, the separating function (E and I) appliestoelementsthatformanintegralpartofthewallsandenvelopeofthecompartment:i.e.thewallsandslabs.

Fortheloadbearingcapacityfunction,itisworthevaluatingallmodesoffailure,suchasrupturebyflexion,byshearingload,bybuckling or rupture of the anchoring of concrete elementreinforcements.

The ISO curve test does not take into account links withneighbouringelements,whichallowstressestoberedistributedtolessexposedsectionsorelements.

Some phenomena, in particular the expansion of the entirestructureundertheinfluenceofhightemperatures,arenottakeninto consideration in the ISO curve test, yet these may bedecisiveinreality.

TheconcreteelementsofbuildingscansatisfyallfireresistanceclassesdefinedbytheEuropeanFireSafetyDirectivewithoutany additional protective measure whatsoever (plaster coating,

intumescentpaint,etc.).

Attention!Thefactthatastructuralelementhaswithstoodafiredoesnotmeanthattheelementhasnotsuffereddamage,orthatthe element does not need replacing. It simply means that thestructural functions of the element were fulfilled under thethermalandmechanicalloadssupported.

If a calculation is made for a required period of fire resistance,there is no need to worry about thebehaviour of the structurebeyondthisperiodnor,afortiori,afterthestructurehascooled

downtoambienttemperature.

The tests include limits: costly, they only allow elements oflimited length to be tested, generally without being able toreproduceattheirextremitiesthetiestothestructure.

To avoid [37] a fireresistance test being necessary for eachconstruction product, calculation methods havebeen perfectedto define the thermal (6.2) and mechanical (6.1) stresses andthereby evaluate the resistance to fire (8.1) of structures madefrom concrete, steel mixed steel/concrete, wood, brick andaluminium. These calculation methods canbe found in the

section of the Eurocodes on firebehaviour. The aim of thesedocuments is to define with a common manner through thewholeEuropethestructureswithstandtothefire.

Basedonthesedesignstandards,anEuropeanproductstandardhasbeen drawn up specifically for each type of element. Thusfalse ceilings, service ducts, faades, walls, valves, concretehollowcoreslabs,etc.haveaspecificstandard.ThisprovisionisnotthatwhichprevailedinBelgiumwhere,previously,alltheseelementsweredealtwithwithinasinglestandard.

The denominations R, E and I are not included in the Belgianbasic standard but are currently included internationally,

notably by the CEN, the European Committee for


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Standardisation. The denomination Rf in hours of the standardNBN 713.020 will be adapted to the denomination REI inminutes, in accordance with CEN standards. The texts havealreadybeenpreparedinthissensebytheFPSHomeAffairs.

At present, furnace tests havebeen standardised at Europeanlevel toensuretheycanbereproduced fromonefurnaceto thenext.

Previously,resultscouldvaryconsiderably[1],forexamplefromtwo to more than five hours for the same hollow core slabelement in different furnaces. By comparing the increases intemperature [5] measured on the exposed face of an identicalelement placed in 14 European furnaces respecting the ISOcurve, the temperature of 800 C is reached after times ofbetween 28and 48 minutes. Belgian furnaces are among themostsevere.

Thedifferencesweredue,amongotherthings,totheradiationofthe flames and the walls of the furnace, to the overpressureimposedinthefurnace,andtothesupportconditions.Belgiumwas the only country to impose such a high gas overpressurevalue (20 Pa). This difference significantly alters the fireresistance times of elements which have a separating functionbut not the resistance of loadbearing elements completelysurroundedbythefire.


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3. Regulations

3.1. European directives andEurocodes.

3.1.1. European directives

Ifwewishtounderstandthefarreachingchangesinthemarketandfireregulations,wehavetounderstandtheoverallcontext.

The Construction Products Directive, the CPD, [2]distinguishesbetweensixessentialrequirements(ERs)forwhichtheMemberStatesareallowedtoregulateconstructionworks:

1. mechanicalresistanceandstability;2. firesafety;3. health;4. hygieneandtheenvironment;5. safetyofuse;6. energysavingsandthermalinsulation.

As its name suggests, the CPD is imposedby the EuropeanUniononPRODUCTSplacedontheEuropeanmarket,deliveredto sites,but NOT on STRUCTURESbuilt on sites with theseproducts: therequirementsrelating tostructures remain withinthecompetenceoftheMemberStates.

ER 2 of fire safety is regulated at federal level in Belgium. TheregulationofER1currentlyrestsonthedecennialresponsibilityof the designer and entrepreneur. ER 6 is the subject of aEuropean Directive on the energy performance of buildingsrecentlytransposedintoourregionalregulations.

This

Construction

Products

Directive

is

one

of

the

new

approach directives enacted following on from the Treaty ofRome of 25 March 1957 establishing the European EconomicCommunity.Themainaimbehindcreatingitwastoremovetheobstacles to the free movement of people, services and goods(and therefore products) between Member States. Aninterpretative document, draftedby the European Commissionin collaborationwith Europeanexperts, is linked to eachof theessential requirements. Following the general objectivesreleased in the interpretative document for the ER fire, thebuilding [107] mustbe designed and constructed such that incaseoffire:

- thepropagationofthefireandofsmokeinthebuildingislimited;

- the structural elements retain their function for apredeterminedtime;

- the fire is prevented from spreading to adjacentbuildings;

- people can vacate thebuilding orbe rescued in someothermanner;

- thesafetyofthefireservicesisguaranteed.

Itshouldbepointedoutthattheprotectionofgoodsaswellasthe preservation of production stops do not in themselvesconstitute objectives of the CPD. The European Commissionleavesitup toeachcountry todetermine the levelofsafety forpeople in their country. The additional information specific toNBNEN199212[107]specifiesthateachcountryisatlibertytoimpose criteria in its regulations which take into account theprotection of directly exposed goods for economic and/orenvironmental reasons. The regional authorities in charge of

economicdevelopmentand those inchargeof theenvironmentmaybe aware of the aspect of the preservation of productionstops and the environment. Obviously these aspects also fallwithinthecompetenceofthebuildingowner(see1.devotedtofiresafetyobjectives).

Still [107] according to this interpretative document nr2, theessentialrequirementcanberespectedbyfollowingthevariouspossibilities for firesafety strategies in force in the MemberStates, such as conventional (standardised fires) or natural(parametrisedfires)firescenarios,whichincludepassiveand/oractiveprotectivemeasuresagainstfires.

The required functions [107] and levels of performancemaybespecified, either in terms of degree of resistance to astandardised (standard) fire, as is the case in Belgium, orbyreferring to engineering firesafety studies to evaluate thepassive and active protective measures. See NBN EN 199112[106](seerequestfordispensationinBelgium)

Supplementaryrequirements[107]concerning,forexample:

the possibility of installing and maintainingsprinklersystems;

theconditionsofoccupationofthebuildingorofafirecompartment; the use of approved insulating or cladding

materials,includingmaintenancethereof

arenot included in theEC1 fire, as theymustbe the subjectofspecificationsemanatingfromthecompetentauthority.

For a long time, the CPD stumbled on perfecting firereactionstandards,sinceeachcountryhasitsownprocedures.However,threequarters of construction products are concernedby firesafety.[12]

Manyconstructionproducts,forexamplehollowcoreslabsandconcrete blocks, are the subject of a harmonised Europeanproductstandard. It issaid tobeharmonisedassoonas it hasan appendix Z and this is included in the European list ofharmonized standards. This appendix lists the variouscharacteristicswhichanyproducermustdeclareinitsCEmark.This mark is affixed to products or included in the documentsaccompanying products. A harmonised product sold withinthe European Economic Area must bear this mark. Thecharacteristics tobe declared must comply with the standardandbecertifiedinaccordancewithattestationsystem1+,1,2+,2,3 or 4. 1+ corresponds to certificationby a third party, while 4corresponds to a simple declaration of conformity by the

manufacturer.


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Since like most Member States Belgium possesses fireregulations, all construction products whose standard isharmonisedmust,inordertobeused,includeintheirmarkingadeclarationrelatingbothtoreactionandresistancetofire.

The product standards refer to a great many test standardspreparedby the European Committee CEN TC 127. They arebeginning to replace the tests described in Belgian standardNBN713020.

ColruytGhent[58]:(sourceERGON)

Thisbuilding has a 3000 m2 car park on the lower level forcustomersaswellasanunloadingbayfordeliveries. Theactualstore is situated above the car park and the staff premises arelocatedonanintermediatelevel.

Thecolumnshavebeenfittedwithvariousaccessoriesallowingboth cellular concrete faade elements and prefabricated fireescapestairwaystobeattached.

TheTTPL840slabsoftheflooroftheshopextendbeyond17mand can take a load of 1200 kg/m2. The roof consists of IVbeams.

The columns of the central axis are fitted with a downpipe forrainwaterdia.160mm.

Thestructurewasinstalledinaroundtwentydays.

3.1.2. The Eurocodes

TheproductstandardsarebasedonEuropeandesignstandards

known as Eurocodes, 58 in number, producedby the TC250Technical Committee of the CEN, the European Committee forStandardisation. It was the European Commission whichdeliveredamandatetodraftthesestandards. Thus,todate,thedesign standards relating to concrete subjected to fire andpublishedby the IBNbetween 1995 and 1999 which apply inBelgiumare:

- NBN ENV 199122 + NAD Actions on structuresexposedtofire;

- NBN ENV 199212 + NAD Design of concretestructuresfirepart;

- NBN ENV 199412 + NAD Design of mixed steel

concretestructuresfirepart;

- NBN ENV 199612 + NAD Design of masonry firepart.

It is more usual to talk of Eurocodes 1, 2, 4 and 6, fire part.These Belgian standards are European prestandards,supplementedbytheirNationalApplicationDocument(NAD).

These prestandards (ENV) will soonbe replacedby Europeanstandards (EN), combined with their national appendix (ANB

forAnnexe

Nationale

Nationale

Bijlage

National

Appendix).

ItshouldbenotedthatthefirstnumberjustaftertheENorENVacronymdoesnotcorrespondtoadate!UnfortunatelytheCENassigned the series 1990 to 1999 to the Eurocodes. Thepublicationdateofthestandardisgivenattheendofthenameofthestandard(seeexamplehereunder).

Whatdothetermsinformativeandnormativeannexesmean?

When an appendix to a standard is made normative, thedesignermustcomplywiththecalculationmethoddescribedinthisappendixifhehastohaverecoursetoit. Ifitispresentedasinformative, the designer, if he wishes to have recourse to it,may draw their inspiration from this appendix, with theapproval of the client and the competent authorities. It isonlycompulsorytoapplyitifrequiredbytheclient.

Each member countryof the CENsets safety levels and classesvia parameters tobe determined at national level (known asNational Determined Parameters, NDP). The nationalappendix to standard NBN EN 199112:2003 Actions onstructuresexposedtofirewillbepublishedthisyear.

WhataboutstandardisationatEuropeanlevel?[13]

The project anticipates providing European Member States,within the near future, with EN standards on calculating thebehaviour in fire of structural works. Within a prescribed timelimit,eachcountrymusttransposethemintonationalstandards.Forexample,intheinformativeappendices,eachcountrywillbefree toadoptdifferentfireloads.Thechoiceofsafetylevelfallswithin the competence of the States. The publication ofapproved fire Eurocodes could see the light in 2007 (BelgianOfficialJournal). We should emphasise that these standardsbecome compulsory onlyby contract or administrative or legaldeed.

NBNEN199212:2005Designofconcretestructures,firepartwaspublishedbytheIBNatthebeginningof2005.


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The European prestandard, coupled with its nationalapplication document (NAD), NBN ENV 199212, is currentlyinforceinBelgium.

The European standard NBN EN 199212:2005 is currentlybeingtranslatedintoDutch.

Itsnationalannexe(ANB)shouldbeavailablethisyearforuseinconjunctionwithconcreteproductstandards.

Aftera

public

enquiry

and

publication,

it

will

enjoy

a

maximum

periodofcoexistenceofthreeyearswiththeENV,attheendofwhichtimetheENVwillbewithdrawn.

3.2. Status of Belgian fire regulations

Safety in the event of fire falls under the responsibility of thebuilding owner. They determine with the architect the activeandpassivemeasuresthatwillprotecttheirbuilding.

3.2.1. General context

Legislating [40] in the field of fire prevention in Belgium is noeasy matter. In legal terms, fire prevention is said tobe anaccessory competence. In common parlance, this means thatthereisnotoneministerinchargeoffirepreventionbutseveral.For this subject area, new building projects are subject toregulationsspreadacrossseverallevelsofcompetence:

1. Thecommunewhich,since1790,hashadthegeneraltask of preventing and stopping fires throughcommunalregulationsandbuildingpermits;

2. TheCommunities,notablycompetentforhotels;

3. TheRegions,notablycompetentforresthomes;

4. The Federal Government, which has successivelyregulated the fire safety of workplaces (RGPT, since1947), hospitals (1979), electrical installations (RGIE,1981)andtallnewbuildings(1972),thenmediumandtall (1994), low (1997) (revised basic standards in2003).

At federal level, the job of determining basic standards forprevention common to one or more categories of construction,

independently of their destination, lies with the FPS HOMEAFFAIRS.Stillatfederallevel,fortheapplicationofcertain

requirements relating to fire prevention, competence lies withotherministersviaotherregulations.Thetableaboveshowstheallocationofcompetencesasanexample.

Moreover, when this regulation is revised, the term basicstandards should disappear in favour of the term GeneralRegulation, so as not to maintain confusion by the termstandards. Astandardsummarisesgoodpracticeinafield. Itonlybecomescompulsoryifestablishedassuchinaregulation.

There

are

[40]

several

sites

containing

detailed

information,

notably: www.previ.be [66], www.previlex.be, www.normes.be[7], www.anpi.be [60]. These sites are full of information.However, it is always wise to check the information publishedonthesesitesandtomakesureitisuptodate.

3.2.2. Basic standards of fire and explosionprevention

3.2.2.1. Field of application and reference date

TheAppendices to theRoyalDecree (RD)of19December1997

[201]

establish

the

basic

standards

in

terms

of

fire

and

explosion

prevention. These must be satisfied by multistorey newbuildings and also, for the single extension, extensions toexistingbuildings.

Until04April2003[40],thebasicstandardsalsoapplied,fortherenovated part, during renovations of existing buildings. Therepeated problems associated with the way in which thebasicstandards had to be applied in case of transformation ledrenovationsofexistingbuildingstobeexcludedfromthefieldofapplicationfromthisdate. Aspecificregulationforrenovationsiscurrentlybeingstudied.

As part of the procedure of granting a development licence,despite the exclusion of renovations, safety measures mayberequired. They will have tobebased on the provisions of thebasic standards. If some provisions of thebasic standards aredifficult to apply to a renovatedbuilding, they canbe reducedand compensated forby others,based on a decision taken atlocallevel(themayor,advisedbyhisfireservice).

The RDs of 94 and 97 do not apply to singlefamily houses,industrial buildings and buildings with up to two levels

coveringatotalarealessthanorequalto100m2.

Federal Communities Regions

FPS HomeAffairs

FPS Employment -Labour

FPSEconomy

FPS PublicHealth

NL FR D Flanders Brussels Wallonia

Hotels Town and country planningBasic standard Legislation onWelfare at Work,RGPT (schoolsincluded)

RGIE - DPC Hospitals etpsychiatricinstitutes

Homes

Table: As an example: distribution of competences in the field of fire prevention in Belgium
http://www.previ.be/http://www.previ.be/http://www.previlex.be/http://www.anpi.be/http://www.anpi.be/http://www.anpi.be/http://www.previlex.be/http://www.previ.be/


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Itisthedateoftheacknowledgementofreceiptbythecommuneof the complete development licence application file thatdetermineswhichversionofthebasicstandardsapplies.

Insummary:[8]

Building

permit

Low

buildings

Medium

buildings

Tallbuildings

Before1972 N/A N/A N/A

22/12/1972 N/A N/A RD04/04/1972includingNBN

713010

1980 N/A NBNS21201,2,3

NBNS21201,2,3

26/05/1995 N/A RD07/07/1994 RD07/07/1994

01/01/1998 RD19/12/1997

RD19/12/1997 RD19/12/1997

04/04/2003 RD

04/04/2003

RD04/04/2003 RD04/04/2003

Table:Referencedatesfortheapplicationofmodifyingdecrees[101,[102],[103],[104].

3.2.2.2. Royal Decree (RD) of 1997

Appendices1to5oftheRoyalDecree(RD)of1997are

1. Terminology;2. Lowbuildings(LB)h25m;

5. Reactiontofireofmaterials.The height limits correspond to the sizes of the fire servicessmall and large ladders. The height (h) in question is thedistancebetweenthelevelofthefloorofthehigheststoreyandthelowestlevelofthestreetssurroundingthebuildingthatcanbeusedbythefireservice.Ingeneral[5],therequirementsare:

2hforTBsandundergroundlevelsofMBs; 1hforfloorsofMBsandLBs; hforroofsofLBs.

Therequirements[20]forbasementsarestricterthanforgroundfloors and upper floors of the samebuilding, give the greater

problemstointerveneintheeventofafireinthebasement.

The provisions of thesebasic standards that apply tobuildingsconcern:

locationandaccessroads; compartmentalisationandevacuation; certainconstructionelements; theconstructionofthebuildingsandevacuationareas; theconstructionofcertainpremisesandtechnicalareas; theequipmentofthebuildings.

The classification for reaction to fire included in appendix 5 ofthe basic standards comprises 5 classes: A0 to A4. The

document also puts forward requirements for reaction to fire

accordingtotypeofpremises. Anewversionofthisappendix,introducing the new European classification, is currentlybeingfinalised.

Specifically, for insulating materials, a correlation table of pastand present reactions to fire was drawn up in two differentversions.IntheabsenceofaconsensuswithintheHighCouncil,twodifferentproposalsweredraftedandsenttotheMinisterforHomeAffairstoallowhimtochooseoneofthem.

Obviously the few architectural provisions tobe retained andincludedbelow cannot replace the complete text of thebasicstandards(110pages)[11]:

The horizontal distancebetween abuilding and an opposingbuildingshallbe6mforLBs,8mforMBsandTBs,exceptifthewallssatisfytherequirementsdefinedforcontiguousbuildings.Thisdistancedoesnotapply tobuildings thatare separatedbyexistingstreetsorlanes,etc.belongingtothepublicdomain.

WallsthatseparatecontiguousbuildingsshallhaveanRfof1hforLBs,2hforMBsand4hforTBs.

Buildingsshallbedivided into compartments whose areashallbe less than 2500 m2, except for car parks. For atriums, thecompartment which extends over several levels must beequipped with an automatic extinguishing system and a heatand smoke exhaust system. The presenceof these installationsallowsthelimitof2500m2tobeexceeded.

Lintels(partbelow the floor),aprons(partabove the floorandbelow the window) and piers (part of faade between twowindows):thesumofthedimensions,asgiveninthefollowingfigure,shallbegreaterthan1m(MBsandTBs)

Figure:apron[18]


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Figure:pier[18]

Even if the external observer does not realise it, glasscurtainwallsmustalsosatisfytheserequirementsrelatingtoapronsandpiers.

Stairwellsandlifts

- For external stairs giving access to an evacuation level: no

resistancetofireisrequiredbutthematerialshallbeofclassA0(noncombustible);

- Stairwellsservingbasementsmaynotbeadirectextensionof those serving levels situated above an evacuation levelexcept in the presence of a wall and Rf door separatingthem;

- For LBs, on each level, communication between thecompartmentandthestairwellshallbeguaranteedbyanRfdoor.

Figure:LBgeneralcase[18]

- For MBs, the landing of the lift(s) maybe included in the

escaperoute;

- ForMBsthatdonothavemorethan6apartmentsperlevel,servedby the same internal stairwell, the shared hall oftheseapartmentsmayconstitutetheliftlock;

MBgeneralcase[18] MB 6apartments[18]

- For TBs, the access landing of the lift(s) mustbe separatefromthelandingsandlocksofthestairwells.Theymustnotbeincludedintheescaperoute,exceptinthecaseslistedinthebasicstandards(complexcaseswith4and6apartmentsperlevelnotincludedhere).

TBgeneralcase[18]

3.2.2.3. Royal Decree (RD) of 4 April 2003

The arrival on the market of new technologies, the noting ofcertaininaccuraciesintheinitialtextandtheamendmentoftheregulationsonotherlevelspersuadedthelegislatortointroduceanewamendingdecree.TheRoyalDecreeof4April2003[202]allowedseveralchangestobemade,relatinginparticularto:

- Existingbuildings:see3.2.2.1above;- Circularstaircasesallowed if treadof24cmon lineof

stairflight;- Boiler rooms: requirements according to power of

heatingsystem;- Lifts:distinctionoftypeswithspecificrequirements;- Electrical installations:availabilityofliftsforpeopleof

reducedmobility;- Fireresistantvalves:new,clearerprovisions;- Behaviour in fire of roofs: according to European

classification, the surface materials of roof coveringsshallbeofclassA1orclassBROOF(t1).

3.2.2.4. The proposed new regulations

3.2.2.4.1. Industrial buildings

New

industrialbuildings

are

not

yet

covered

by

the

federal

regulationsonnewbuildings.Theirregulationwasthesubjectof


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very long discussions to end up at a draftbasic standard, thefutureAppendix6. ItwasneverpublishedintheformofanRDbut most fire services are aware of the document and, in theabsenceofanapplicableregulationinthisarea,useittodrawuptheirpreventionreportsinrelationtoindustrialbuildings.

Among other things, this draft included a classification from astandard on automatic extinguishing systems or sprinklersbased on the type of activities in thesebuildings. This RD was

rejectedby the Council of State, which argued namely that thetypeofactivityinthesebuildingsfellwithinthecompetenceoftheRegionsandnottheFederalauthorities.

To make up the lack of regulation in this area andbased on aproposal from Agoria and Technum, passed onby the FEB, anadhoc group of the High Council for Safety against Fire andExplosion has drawn up a new draft of annexe 6 which iscurrently being approved. It is based on a classification ofindustrialbuildings according to their characteristic fire loaddensity.Itestablishes:

- a maximum permissible calorific load per compart

ment,fromwhichisdeductedthemaximumareaofthecompartments,

- a fire resistance for the walls of compartments as wellasforotherstructuralelements,

- minimumdistancesfromneighbouringbuildings,

- the requirements to be satisfied for evacuating theoccupantsandthesafetyoffireteams.

Appendix 7 including the general objectives has beenabandoned.

3.2.2.4.2. Faades

Rulesforthedesignoffaadesarecurrentlybeingstudiedbyaworking group of the High Council. They will detail theprovisionsalreadyincludedinthecurrentbasicstandards.

3.2.2.4.3. Wall crossings

Recommendationsontheconstructionofwallcrossingsbyfluidor electricity conduits have alreadybeen distributed to the fireservicesintheformofacircular.Aprocedureforamendingthebasic standards has already been begun. It includes theserecommendations.

3.2.3. Building permits - fire resistance

Currently, fire resistance is determined either by tests infurnaces to NBN 713020 orby calculation, as allowedby thebasic standards (appendix 1 of the RD of 191297), inaccordancewithacalculationmethodapprovedbytheMinisterforHomeAffairs.

Tousethiscalculationmethod,thefollowingmaybetakenintoaccount:

examinationofconventionalfirescenarios;

examination of natural fire scenarios, with examination oftheroleofextinguishingsystems,firemenandfiredetectionsystems;

As of today, no method has yet been approved. TheDispensations Commission authorises them on a casebycasebasis. In practical terms, designs made with the ISO curve areacceptediftheyareproducedonthebasisofourNADpart12oftheEurocodesandifthesehavebeencorrectlyapplied. Therevision of the fire basic standards should standardise thisprocedure. Designofficesverify therequired fireresistancebycalculation. It is mentioned explicitly on construction plans.

Architects

and

building

owners

concentrate

on

technical

compliance with the provisions of the regulations and therequirementsofboththefireservicesandinsurancecompanies.

Priortothegrantingofthebuildingpermit[8],theplansofthefuture construction are sent to the locally competent fireservices. Thesethenprovidearecommendation,intheformofareport, which will be appended to the building permitapplication for a decisionby the townplanning department ofthe commune concerned. At the end of the work, the fireservices make a final visit to check that the construction doesindeedcomplywithwhatwasspecifiedontheplanandthatthebuildinghasnomajorshortcomings.

According to the RD of 1997, doors have their fire resistancecertifiedby the BenorATG mark. They mustbe installedbyfittersapprovebyourMinisterforHomeAffairs.

This dual requirement was quashedby the Council of State in2004, following a complaint concerning the use of approvedfitters. TheparagraphoftheDecreelistingthetworequirementswas removed at a stroke, while the safety requirement relatingto BenorATG certification couldbe remained. The FPS HomeAffairshasdraftedatexttofillthecurrentvoid.

3.2.4. Fire detector regulation for residential

accommodation+Scandinaviancountries

IntheScandinavianandAngloSaxoncountries,smokedetectorshave longbeen requiredbecause many houses were made ofwoodandtheneedforwarningseemedmorebasic: whereverdetectors are fitted, there hasbeen an average reduction in thenumberofdeathsandseriousinjuriesof80%.

Smokedetector(source[8])


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Issued in 2004, the decree of the Brussels government requires,fromJuly2005,smokedetectorsinallhousesletintheBrusselsRegion.

InWallonia,since20112004,allnewhousesmustbefittedwithsmoke detectors, whether let or occupiedby their owner. Allotherhousesmustalsobefittedwithdetectorssince01072006.

The detector must carry the CE label and be approved byBOSECoranequivalentEuropeanbody. Itmustbeguaranteedfor5yearsbythemanufacturer.Installationisundertakenbytheowner and any replacement ofbatteriesby the tenant. In thisrespect, the choice of lithiumbatteries with a life of 5 yearsallows you to leave their replacement to the occupants, whichcan oftenbe uncertain. When thebattery reaches the end of itslife,thedeviceemitsanacousticwarningsignal.

To cover their furniture and houseby fire insurance, everyoneagreestogive300,500,600EURO.

To protect people, thebasic price of an approved detector isaround tenEUROS.Itwouldberidiculousand irresponsible tothinktwiceaboutmakingthisinvestment.

In Flanders, there are no regulations relating to detectors inhouses.

InFrance,detectorsarenotyetcompulsory.

3.2.5. Old buildings

Oldbuildingsaproblemalltheirown[8],[9],[10]

On Wednesday 20 February 2003, during the night, a fire isdeliberately started in an apartment block in Mons. Theconsequencesaredire:sevendead,includingachild.

Thisfirecapturespublicopinion:thepublicfeelsconcernedand,the day after the drama, a lot of housing and managementcompanies send requests for inspections to the fire services todetermine whether theirbuilding satisfy current safety criteria.They also want to supplement the training of their communityofficers,conciergesorotherpeopleinpositionsofresponsibility.In Brussels alone, in a matter of weeks, more than 22000applications are recorded. Others are still regularlyreceived.

Even if today a recommendation from the fire services isattachedtobuildingpermitapplicationsandinthiscasehastheforceoflaw,thisisonlythecasefornewbuildings. Andyetthisiswheretheproblemlies:mostrequestsforinspectionsconcernoldbuildings, as they no longer satisfy current fireprevention

requirements. Therisksarethereforerealinthesebuildingsandwemustnottakethemlightly,asdemonstratedbythedramaofthe fire in Mons. The main buildings concerned are socialhousingbuildings, that are often grouped together to form acity. The problems causedby cheap construction are madeworsebytheproblemofvandalism,whichcontributesasmuchto the causes of fires, often deliberate, than to the dilapidatedstateofthebuildings.Forexample,anynewextinguishersfittedwouldberippedoffthenextdayorusedbyamalicioushand.

Unfortunately, none of the legislation mentioned above canbeappliedretroactively:allbuildingsbuiltbefore1972,whichoftenpresent the greatest risk, are not governedby any regulations,

exceptforanyextensionsbuiltatalaterdate.


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4. Protection and risks

4.1. Fire: risks, factors, origin andpropagation

In a wellprotectedbuilding there is abalancebetween danger

andprotection.Theriskisthereforedefinedbytherelationshipbetween danger and protection. The danger is greater in tallbuildingsbecause,more than in otherbuildings, the firehas toattackfromtheinside.Itisalsogreaterinbuildingsthatcontainpeople with reduced mobility, whom it is more difficult toevacuate. The greater the danger, the stricter the safety rulesmustbe.

Thefactors[38]toconsiderinthedevelopmentofafireare:

- theprobabilityofafirestarting;- theintensityofthefire;- thespeedatwhichthefiremayspread;

- theexistenceofspecificrisks(toxicproducts).

Theprobabilityofafirestartingdependson:

- heatingsystemsandelectricalequipment;- thepresenceofinflammablegas;- certainindustrialchemicalprocesses;- thepresenceofdustthatcouldcreateexplosions.

Withregardtothelastpoint,wastesuchaswoodshavings,dustetc. mustbe removed regularly to counter a serious danger offire. We should also mention the spontaneous combustion ofrags saturated in oil, the autoinflammation of steel woolbybatteries,etc.

Theoriginofthefiredangermaybe:- internal,linked:

tothebuildingitselfanditscontents; to the activities carried on therein (industrial

activities); to the people who occupy the building

(smokers,waste).- external,linked:

to adjacent buildings (via windows, forexample);

toneighbouringinstallations(liquefiedgas); togasmainsbeneaththepublichighway.

Itsdevelopmentinthecompartmentislimitedby:

- the choice of materials in the buildings (see 2.4reactiontofire)and

- the reliability of the technical activeprotectioninstallations such as detectors, alarms, sprinklers, heatandsmokeexhaustsystems.

Its propagation beyond the compartment is limited by theresistancetofireofthecompartment(passivesafety).

4.2. Passive and active protectionand human behaviour

Preventive measures are classically divided into passive andactivepreventivemeasures:

thefirstareputinplacewhenthebuildingisconstructedandareoperationalatalltimes;

the second may be put in place during or afterconstructionofthebuildingandonlybecomeoperationalintheeventofafire.

4.2.1. Passive protective measures -compartmentalisation

Concrete occupies a very broad area in the field of passiveprotectivemeasures. Thanks to itsrecognised fireresistance, itallowstheconstructionofhighlysecurecompartmentalisation,thus preventing the fire from spreading. Thiscompartmentalisationallowsoccupantstobeevacuatedortaken

safely to another compartment. It facilitates the access of theemergency services, thereby contributing considerably to theirsafety while fighting the fire. Compartmentalisation shouldbestudiedwhendrawingupthebuildingplans.

Concreteallows thecontinuityofactivities in installationsof

vitalinterest.

Continuity is paramount inbuildingsof public interest such aspower stations, railway stations, hospitals, general governmentoffices.

In warehouses, hotels, industrial sheds, office complexes,distribution centres, fires interrupt not only the running of theenterprisesoperatingthembutalso:

- theservicetothepeoplewhousethem

- theproductivityoftheenterprisesororganisationsthatrevolvearoundtheactivitiesoftheaffectedenterprise.

Apart from its loadbearing function, concrete combines fire

protection,thermalprotectionandsoundprotection

The interior walls, exterior faades and floors ofbuildings aresubject not only to mechanical loadsbut also to the thermalstressesoftheclimate,ambientnoiseandfires.

Thefigurebelowshowstheactionsonacompartmentwallandtheassociatedpropertiesnecessitatedbytheseactions,fulfillingtheappropriateprotectivefunctions.


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(Neck,1999)

The figurebelow repeats the properties of the materialand thestructural properties of the components thanks to which thelatter satisfy the requirements of fire protection, thermal

protectionandsoundprotection.

Firepreventionisbasedon

- achoiceofmaterialswithagoodreactiontofire;- theuseofcompartmentalisationenablingthefiretobe

confinedintheplaceitstarted;

- sufficient exists to evacuate people: number of exits,width,continuousbalconies,etc.

The weak points of compartmentalisation cannotbe detailedhere (consult [5]). They involve firstly doors (BenorATG): weshallcomebacktothispointinthechapteronregulations.Theyalso concern crossings for ducts and conduits, localdeforcements (switches etc.), basements (air supply), faades(aprons+lintels+balconies)aswellasroofs.

Ifitisnotclosed,thebestfiredoor[5]isuselessinafire.Whenthe legislator requires doorclosers, it is often observed that inreality, these doors are kept open to facilitate the use of thebuilding. BS 7974: PD7 [111] also provides reference valuesrelatingtothereliabilityofthesedoors:theprobabilityof thesefiredoorsbeingblockedwhileopen is30%. The probability ofautomatic doors not closing correctly is 20%. The use [5] ofclosing devices, linked to a detection system, allows thissituation, which endangers the entire desired effect ofcompartmentalisation,tobeavoided.

NonrefacedwallinanEIwall,attheleveloftheheatingducts

crossingit(source[8])

Avoid!AnopeninginanEIwallforpassingelectriccablesthrough

andwhichhasnotbeenrepointed(source[8])

non-combustible material

high resistance + good

dimensional stabilityfire protection

thermal conductivity

low thermal diffusivity thermal protection

high resistance to water

high density sound protection

high flexional rigidity

good sound absorption


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Walkwaysrunningalongtheentirefaadeofthebuilding(source[8]).

Thesecontinuousbalconiesconstituteescaperoutesforpeople.

4.2.2. Active protective measures

TheactiveprotectivemeasurestakenintoaccountbyFireSafetyEngineeringallowfirestobetackledby:

automaticdetectionlinkedtoanalarmsystem;

extinguishingsystems(extinguishers,automaticsprinklersystemenablingthesizeofthefiretobecontrolled);

heat and smoke exhaust systems (HSE): canbe partlypassiveandpartlyactive;

theonsitefireteams,thefireinterventionservices.

Distinctionbetweenannouncement,alertandalarm

AsmentionedinthefinalparagraphofAppendix1totheRoyalDecree of 1997 onbasic fire standards, Belgium distinguishesbetweenannouncement,alertandalarm:

- the announcement which is the message to the fireservicesthatafirehasbeendiscoveredordetected;

- the alert which is the message sent to the peopleconcerned in the organisation that a fire has beendiscoveredordetected;

- thealarmwhichisthemessagetotheoccupantsofoneor more compartments that they must evacuate their

compartment.

Smokeextractionopeningsatthetopofthestairwell(source

FEBELCEM)

Thiscorridorcontainsalargenumberofelementsofactiveprotection:

alertingunit,hosereel,signallingpanel,smokedetector,emergency

lighting(source:FEBELCEM)

The performance of sprinklers [41], normally highlighted fortheir operational reliability, is evaluated in the USA inlaboratory test conditions where, in 96 to 99% of cases, thesprinkler is activated when the temperature is reached at headlevel.Butthisapproachdoesnotconsiderrealsituations,wherethis same level of performance of controlling or extinguishing

thefireisnotachieved.ThestatisticsreportedbyM.RohroftheNFPA in September 2001 in U.S. Experience with Sprinklersindicate that, for fires of such a size that the sprinklers shouldhavebeen activated, the system failed in its mission in 13% ofapartments,17%ofhotels,20%ofhospitalsandoffices,26%ofpublicplaces,withanationalaverageof16%failures.(Weshallreturnlatertothevalueofsprinklerreliability!).Basedonthesefigures,theactualperformanceistherefore10timeslowerthanannounced.

Howcanwedefinethesuccessofasprinklersystem?

The area of operation or of calculation of the sprinklers variesaccordingto therisk.Riskclassesaredefined for low,ordinary(OH)orhighrisks.Eachclasshasasprinkledareathatmustbe


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kept under control. This means that the fire must not spreadbeyondthisarea.ThefollowingtablefromNBNEN12845givesthe definition of these areas of operation, combined with anumber of sprinkler heads and a minimum flow rate persprinklerhead:

Riskclasses

Numberof

sprinklerheads

Areaofoperation

(m2)

minimumflowratepersprinklerhead

(l/m2/min)

Low 1/21m2 84 2,25Ordinary 1/12m2 72to360 5

HighexceptHHP4

1/9m2260 7,5to12,5

Sprinkler(source[8])

In Canada, the regulations in Ontario have led to the use ofsmoke detectors and fire alarms in combination with

compartmentalisation.Theprincipleisthatfirealarmsprovideasuitable evacuation time and therefore the expenses andproblems associated with sprinkler failures are removed. If theregulationsaremaintainedastheyare, it isbecause ithasbeenshownthat,forthesafetyofpeopleandgoods,thecombinationof fire alarms and fireresistant compartmentalisation presentsnomoreofariskthatthatoffirealarmsandsprinklers.

AnindepthdiscussionoftheuseandperformanceofsprinklerscanbefoundinAppendix1(seeCha

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