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Chapter1.Introduction
Regardingfiremodels9twopossibilitiescanbedistinguished.nominalfire
curVesandnaturalfires.TheformerconsistsoftheISO834curVe(themostcom-
mon9calledthestandardfirecurVe)9butalsothehydrocarbonfirecurVeandthe
eXternalfirecurVe.AllofthemareincludedinEurocode1991-1-2[20]andthey
canbeusedtoeValuatethethermaleXposureofstructuresinfire.Naturalfire
modelsarealltheotherthannominalcurVesapproaches.Naturalfiremodelsare
usedtodescribethefirebothqualitatiVelyandquantitatiVely.Contrarytonominal
firecurVes9naturalfiremodelstakeintoaccountthespecificconditionsthateXist
inthedesignedobject9i.e.thermalparametersofwalls9Ventilationconditions9fire
load.
Table1.Possibletypesofdesignapproacheswithrespecttostructuralmodel.
Simplecalculation
Advancedcalcula-
Prescriptiveap-
tionmodels
proach
models
↓PBrformIncB-bIsBdstructuralfireengineeringapproaches↓
Element
++
++
+
Substructure
++
_
+
Structure
__
++
_
Thechoiceofthefiremodelissomehowrelatedtothechosenstructuralmodel.
Accordingto[140]9thefirstcorrespondencebetweenthemodelofthermaleXpo-
sureandthestructuralmodel(element9substructure9structure)wasgiVenbyWit-
teVeenin1983.WitteVeen’sfindingswereadoptedbyPurkissandfinallyrear-
rangedbyotherresearchers.Theresultedtablesofapplicationdomainofdifferent
designmethodsunderthefiresituation(Table2)canbefoundinseVeralpublica-
tions9i.e.[519170].
TheaboVestrategyandapplicationproceduresareallgiVeninEurocode
1991-1-2[20]inastraight-forwarddecisiontree(Figure1.1).Nomatterwhatde-
signprocedureischosen;whetheritistabulateddata9asimplecalculationmodel
oranadVancedcalculationmodel9thereisalwaysone9physicallybasedscheme
ofanalysisofstructuresinfire.Regardlessofthefireconditionorfiremodeland
materialofthestructure9alltheanalysesmustconsistofthreeparts.(1)firedefi-
nition9(2)determinationoftemperaturefieldinsidethestructure9(3)determina-
tionofmechanicalresponseofstructure.ThereareseVeralmethodsforeValuation
ofthosethreeinherentingredientsofeachanalysis9whicharepresentedinFigure
1.2.
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