Urban fire risk: Evaluation and emergency planning

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Available

online

at

ScienceDirect

www.sciencedirect.com

Cultural

HELP

2014

Special

Issue

Urban

ﬁre

risk:

Evaluation

and

emergency

planning

Tiago

Miguel

Ferreira

a,∗

_,

_Romeu

_Vicente

a,1

_,

_{Jos ´e}

_{Ant ´onio}

_Raimundo

_Mendes

_da

_Silva

b,2

_,

Humberto

Varum

c,3

_,

_Aníbal

_Costa

a

_,

_Rui

_Maio

a,4

a_RISCO_-_Department_of_Civil_Engineering,_University_of_Aveiro,_Campus_Universit´_ario_de_Santiago,_3810-193_Aveiro,_Portugal

b_LAETA_-_Department_of_Civil_Engineering,_University_of_Coimbra,_Rua_Lu´ıs_Reis_Santos_-_P´_olo_II_da_{Universidade,}_3030-788_Coimbra,_Portugal c_CONSTRUCT_-_Department_of_Civil_Engineering_-_Structural_Division,_Faculty_of_Engineering_of_the_University_of_Porto,_Rua_Dr._Roberto_Frias,_4200-465 Porto,Portugal

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received26November2014 Accepted21January2016 Availableonline7July2016 Keywords:

Oldcitycentres Firerisk ARICAmethod Emergencyplanning Oldbuildings

a

b

s

t

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Themanagement,preventionandmitigationofurbanrisksareassumedaspriorityactionswithinthe frameworkofanyrehabilitationandrequalificationprocessattheurbanscale,particularlyinthecase oftherehabilitationandrefurbishmentofoldcitycentres.Inthemostspecificdomainofurbansafety, seismicandfirerisk,whichcancauseseriousconsequences,arepartofthecollectivememoryofseveral communitiesandmustbeinevitablyhighlighted.Theseverityoftheresultingdamagesisamorethan validreasontostronglyvalueprevention,planningandmitigationstrategies,limitingtheirconsequences andguaranteeingpermanentimprovementactions.Intheviewoftheabovementioned,andinthescope ofaresearchprojectcarriedout,anewurbanfireriskassessmentmethodologywasdevelopedand appliedtotheoldcitycentreofSeixal.Thissimplifiedmethodologyisbasedonapreestablishedmethod designatedARICA.Over500buildingswereassessedusingthismethodology,andtheresultswere spa-tiallyanalysedusinganintegratedgeographicalinformationsystemtool(GIS).Itisworthnotingthatthe integrationoftheriskresultsintoaGISplatformisavaluablesteptowardstheriskmitigationataurban scale,allowingcitycouncilsorregionalauthoritiestoplaninterventionsonthebasisofaglobalspatial viewofthesiteunderanalysisleadingtomoreaccurateandcomprehensiveriskmitigationstrategies thatsupporttherequirementsofsafetyandemergencyplanningincaseofurbanfire.

1. Introduction

1.1. Framework

Oldcitycentresareparticularareasofvitalimportancedueto

theirvaluablehistorical,architectural,culturalandsocialheritage,

whichshouldbepreservedandconstantlyvalued.Inthissense,it

isessentialthatinstitutionsresponsibleforsafeguardingthis

her-itageandthepopulationwhobeneﬁtfromit,joinforcesandwork

togetheronthepreventionofﬁreriskwithintheseareas[1].

Theuniquefeaturesofoldcitycentresanditsbuildingstock

areclearlydistinctfromrecenturbanareas,favouringtheignition

∗ Correspondingauthor.Tel.:+0035123437004;fax:+00351234370094. E-mailaddresses:tmferreira@ua.pt(T.M.Ferreira),romvic@ua.pt(R.Vicente),

raimundo@dec.uc.pt(J.A.RaimundoMendesdaSilva),hvarum@fe.up.pt(H.Varum),

agc@ua.pt(A.Costa),ruiamaio@ua.pt(R.Maio). 1_Tel.:₊₀₀₃₅₁₂₃₄₃₇₀_04;_fax:₊₀₀₃₅₁₂₃₄₃₇₀_094. 2_Tel.:₊₀₀₃₅₁₂₃₉₇₉₇_206;_fax:₊₀₀₃₅₁₂₃₉₈₃₂_969. 3_Tel.:₊₀₀₃₅₁₂₂₀₄₁₄_882;_fax:_+1446.

4_Tel.:₊₀₀₃₅₁₂₃₄₃₇₀_04;_fax:₊₀₀₃₅₁₂₃₄₃₇₀_094.

andpropagationofaﬁre.Severalfactorshavebeenidentiﬁedas

potentialcontributorsforincreasingﬁreriskintheseareas:

com-bustiblematerialspresentintraditionalbuildings,thehighdensity

ofbuildingsinoldcitycentreswithnarrowunobstructedstreet

widths, the wallsharingbetween adjacentbuildings, the

inad-equate adaptationof buildingstonon-residential purposes, the

proliferationofunoccupiedorderelictbuildingsfrequentlystoring

largeamountsofcombustiblematerialsandmainly,theexistence

ofoldelectricalinstallationswithlackofmaintenance,whichisone

ofthemaincausesofﬁreriskofoldbuildingstock[2].

Throughoutworldhistory,therearemultipledevastatingﬁre

exampleswithcatastrophic consequencesinboth economyand

heritage.The1666greatﬁreofLondon,andthe1871ﬁreofChicago,

aretwoofthemostsigniﬁcanturbanﬁreevents,leadingtothe

nearlycollapseofbothcitiesandtohumanlossscalewithno

prece-dentsinhistory.InPortugal,the1988Chiadoﬁre,affectingthis

importantwarehouseandcommercialareaofLisbon(seeFig.1),

remainsasoneofthemostmarkingﬁreeventinthecountry,

lead-inginclusivelytothecreationoftheﬁrstPortugueseMinisterial

OrderNo.426/89of6thDecember,entirelydedicatedtothismatter

[3].Although,noothersimilarorcomparableeventhasoccurred,

http://dx.doi.org/10.1016/j.culher.2016.01.011

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Fig.1. Chiadoﬁreduringbothpropagationandextinctionphase[8,9].

ﬁreriskinoldcitycentresisrecognisedbycitizensand

responsi-bleentitiesasaseriousproblem.In2010,Coelhohasdevelopeda

comprehensiveworkonbuildingconservationandrehabilitation

fromthepointofviewofﬁresafety,identifyingthemostcommon

issuesfoundinourbuildingstockandsuggestingsomesolution

toovercomethosedeﬁciencies[4].Althoughﬁreriskassessment

methodologiescontinueatanearlystageofdevelopmentinrespect

tolarge-scaleassessmentanimportantcontributionwasrecently

givenbyMagalhães[5]whichmayenhancedevelopmentandbring

attentiontoﬁresafetyinbuildingswithinurbanareas,throughthe

developmentofanITtooldesignatedFIREcheck,gearedtowards

theorganisation,planninganddatastorageofﬁresurveyingand

inspectionworkofbuildings. Moreover,a handbookcontaining

guidelinesandprocedurestocarryoutduringﬁresafetysurveying

work has also been developed by [5]. This tool was

compre-hensivelyreviewed and optimisedby Barral [6] toincorporate

theself-protectionpracticesand measuresdeﬁnedinthelatest

nationalﬁresafetycode[7].

1.2. Researchaims

Themain goalof this researchwork is focusedon

develop-ingalarge-scalesupportingtoolforemergencyplanningdirected

mainlytowardstooldcitycentres.Inaﬁrstphase,theSeixalcase

studyallowedtoidentifyandcollectthemainﬁreriskvulnerability

sourcesandthen,inasecondphase,tousethesedataasinputfor

thedevelopmentandapplicationofthenewmethodologytoassess

urbanfirerisk.Thefirstphaseofidentificationanddatacollection

wasperformedthroughagroupofcoordinatedﬁeldinspections

identifyingtheprincipalsafetyfactorsagainstﬁreriskinhistorical

buildings,whichwerestoredinalinkeddatabaseusedinaGIStool

environment.

2. Methodofresearch:ﬁreriskindex

Fire risk assessment methodologies currently available are

scarceandthegreatmajorityofthemweredevelopedexclusively

fortheevaluationofsingleandrecently-builtbuildings,therefore

beingunsuitablefor application tooldmasonry buildingsor at

larger scales. Even though, four different existing

methodolo-giesshouldbelisteddue totheir characteristics,which canbe

in a broad sense approximatedto the old city centres reality:

the Gretener method; the FRAME method; the FRIM method

and the ARICA method [10]. All the referred methodologies

havetheirapplicabilityscaleasa commondenominator, which

is directed to single buildings or at most to building

aggre-gate assessment. Nevertheless, ARICA method presents a clear

advantagewhencomparedwiththeremainingones,itismuch

moreﬂexible interms ofmethodologicalformulationsallowing

that, with some modiﬁcations, it can be used to assess either

old or recent buildings. This is the wholepoint of developing

an expeditious methodology on the same base as the scoring

Table1

Globalfactors,sub-factorsandpartialfactorsdeﬁnition.

Globalfactors Sub-factors Partialfactors,PFij

Globalrisk factor,FGR

Fireignition,SFI Buildingconservationstate

(A1)

Electricinstallations(A2) Gasinstallations(A3) Fireloadnature(A4) Firepropagation,SFP Gapbetweenaligned

openings(B1)

Safetyandsecurityteams (B2)

Firedetection,alertand alarm(B3)

Firecompartmentalisation (B4)

Fireloads(B5) Evacuation,SFE Evacuationandescape

routes(C1) Buildingproperties(C2) Evacuationcorrection factors(C3) Globalefﬁciency factor,FGE

Firecombat,SFC Buildingexternalﬁre

combatfactors(D1) Buildinginternalﬁre combatfactors(D2) Securityteams(D3)

methodologydevelopedbyVicentefortheseismicvulnerability

assessment of old masonry buildings at the urban scale [11],

which is essentially based in qualitative criteria. Aiming the

mentionedgoals,anewsimpliﬁedproposalhasbeendeveloped

withbasisonthesameprinciplesoftheoriginalARICAmethod,

butthistimeadaptedtothealreadyidentiﬁedneeds.

By exploiting information and researchcollected duringthe

extensiveinspectionphase,itwaspossibletodeterminetheﬁre

riskindex,FRIamongotherindicators.Pleasenotethatwiththis

new proposal the authorsdo not want to disregard the

origi-nalARICA method,butassumeit asalarge-scalereworkedand

redeﬁnedassessmenttool,performinganinitialandreliable

esti-mation, and highlighting constraints in need of more detailed

assessmentmethodologies.Thus, astheoriginalARICA method,

thenewﬁrerisksimpliﬁed methodologyis basedontwo main

factors:theglobalriskfactor,FGR,andtheglobalefﬁciency

fac-tor, FGE(see Table1).The ﬁrst is divided in three sub-factors

devoted to evaluating the ﬁre ignition phase, the propagation

phase and the buildingevacuation phase. The globalefﬁciency

factor, FGE, is associated just to one sub-factor evaluating the

ﬁrecombatphase.Thefoursub-factorshavethesamenumerical

weightinthecalculationoftheFireRiskIndex(FRI).However,the

mentioned sub-factors approach the generality of the aspects

relatedtoﬁrepreventioninoldmasonrybuildings,followingthe

wholeeventfromtheﬁre ignition,propagationand evacuation

capacity,toﬁrecombatandextinguishing.Thesub-factors

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Table2

ValuesofthegasinstallationconditionsforpartialfactorPFA3.

Gassupplyingtypeandsiteconditions PFA3

Pipedgas – – 1.00

Gasreservoir – – 1.10

Gascontainers External installation – 1.20 Internal installation Well-ventilated compartment 1.50 Non-ventilated compartment 1.80 Table3

Valuesofthedetection,alertandalarmﬁresystempartialfactorPFB3.

Firedetection,alertandalarmsystems Codecompliance

Equipment/devicetype PFB3

Doesnotrequire Thereisanautomaticﬁre detectionsystem(automatic detectors)

0.50

Thereisamanualﬁredetection system(alarmoperatorbuttons)

0.90 Require

Equipmentinaccordancewith ﬁrecoderequirements

1.00 Thereisnomanualﬁredetection

systemwithalarmoperator buttons

1.20

Thereisonlyamanualfire detectionsystem,whenfirecode requiresanautomaticfire detectionsystemaswell

1.80

Thereisnoautomaticﬁre detectionsystem

2.00

functionoftheinspectioncriteriaandweredeﬁnedbasedon

ana-lyticalhierarchyprocess.Asinterventionsinoldcitycentresshould

betargetedatreducingboththelikelihoodofﬁreoccurrenceand

propagation,thesetwo sub-factors,SFI and SFP,are affectedby

aggravatingcoefﬁcients1.20and1.10,respectively.Thevalueof

eachsub-factorisobtainedasthesumofallthepartialfactor

val-ues.Inturn,thesefactorsevaluatedetailedfeaturesassociatedto

eachsub-factor,suchasthestateofpreservationofthebuilding,

electricalandgasinstallationsandtheﬁreloadnature,relativeto theﬁreignitionsub-factor,SFI.

Belowisprovidedthedeﬁnitionofthreeofthepartialfactors

speciﬁedinTable1–PFA3,PFB3,PFC1andPFD1–,corresponding

todifferentsub-factors.Thevaluesassociatedtothepartial

fac-torPFA3,concerninggasinstallationandsupply,arepresentedin

thefollowingTable2.Furtherinformationregardingthe

deﬁni-tionandcorrespondingvaluesofalltheotherpartialfactorscanbe

consultedin[12].

ThepartialfactorPFB3relatedtodetection,alertandalarmﬁre

systemshasagreatinﬂuenceoverthedevelopmentand

propaga-tionofﬁreevents.Thepresentﬁrenationalcode[13]establishes

twodifferentalarmﬁreequipment/devices,automaticdetectors

andalarmoperatorbuttons(manualdetectors),beingthelast

nat-urallyfarlessefﬁcient.ThefollowingvaluesinTable3weredeﬁned

toassignthepartialfactorPFB3.Wheneverthesedetection,alert

andalarmequipmentisnotdemandedbythepresentﬁrecode,one

mustfollowtheoriginalARICAmethodologyprinciples[14].

More-over,thevalueofthispartialfactorshouldbeconsideredequalto

1.00,havingthereforenoinﬂuenceovertheﬁrerisk,wheneverthe

existingsafetymeasuresmeettheﬁrecoderequirements.

ThepartialfactorPFC1considersallfeaturesconcerning

build-ingevacuationconditionsandescapingroutes,fromclearwidthsof

bothhorizontalandverticalevacuationandescaperoutes,to

win-dowsanddoorswidths,numberofavailableexits,slopeofvertical

Table4

CoefﬁcientvaluesoftheevacuationandescaperoutespartialfactorPFC1.

Conditionsofevacuationandescaperoutes PFC1

Widthsofcorridors/pathsandopeningslowerthan 0.90m

0.25 Numberofexitslowerthantheminimumregulatory

required

0.25 Slopeofverticalescaperouteshigherthan45◦ _0.25

Nonexistenceoflight-signallingemergencysystems whenrequired

0.25

Table5

Featuresandvaluesfortheaccessibilityparameter. Accessibilityandevacuationrouteconditions Height [m] Width [m] Clearheight [m] Slope[%] Accessibility parameter value ≤9.00 ≥3.50 ≥4.00 ≤15.00 1.00 ≥3.50 ≥4.00 >15.00 1.50 >9.00 ≥6.00 ≥5.00 ≤10.00 1.00 ≥6.00 ≥5.00 >10.00 1.50 Table6

Featuresandvaluesfortheexternalﬁrehydrantsparameter. Conditions

Distancefromtheﬁrehydrant Existenceofwall hydrants Firehydrants parametervalue ≤100m No 1.00 >100m Yes 1.50 No 2.00

escaperoutesandemergencylightsignagesystems,whenrequired.

Onceagain,incomparisontotheARICAmethodology[14],the

def-initionofthispartialfactorcomprisesamoresimpliﬁedapproach.

Thus,topartialfactorPFC1isassignedaninitiallowerlimitvalue

equalto1.00,towhicheventuallyaddedoneormoreofthe

follow-ingcoefﬁcientsrelatedtoevacuationandescaperoutes’inherent

conditions(inTable4).Itisworthnotingthat,alsointhiscase,the

conditionspresentedinTable4weredeﬁnedinaccordancewith

thePortugueseﬁrecode[13].

Fromthelastgroupofpartialfactorsassociatedtoglobal

effi-ciency, FGE, the definitionof the buildingexternal fire combat

partialfactorPFD1comprisesthearithmeticaverageofthe

follow-ingthreeparameters:buildingsaccessibility;externalﬁrehydrants

andwatersupplyreliability.Accessibilitiesareofgreatimportance

forﬁrebrigadesintacklingﬁres,sinceitgivesadecisive

contribu-tiontoﬁredevelopmentandpropagation,asalreadymentioned.

Inthissense,Table5bellowpresentsthefeaturesandconditions

neededtoevaluatethisparameter.Inthecaseofroutewidthsor

clearheightsbelowtherangedvalueslistedinTable5,this

acces-sibility parametermust beassigned equal to2.00, astheseare

consideredtwopreponderantassessmentconditions.

Inrespecttohydrantsassessmentparameter,thenationalﬁre

codedemandstheexistenceofﬁrehydrantsatamaximum

dis-tanceof30metersfromeverybuildingexit.Consideringhistorical

city centre mesh one can easily understand that this

require-mentisunreasonableand thus,thereferred maximumdistance

wasassumedinlinewiththisreality,setas100metersforthe

proposednewmethodology.Thefollowing Table6outlines the

admissiblevaluesreferringtoexternalﬁrehydrantsparameter.If

ﬁrstinterventionwallhydrantsaremadeavailable,thevalueof

thisparameterisreducedonlyinthecaseofdistancesfromﬁre

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Table7

Referenceriskfactor,FRR,determinationfordifferentbuildingusetype.

Referenceriskfactor Residential Serviceorindustrial spaces,librariesand archives

FRR 0.915+0.25×FCa 1.10+0.25×FCa a_F

Cisthecorrectionfactorandcanassumethevaluesof1.10,1.20or1.30,for buildingswithupto3,upto7ormorethan7ﬂoors,respectively.

Thewatersupplyreliabilityparameterisconsideredequalto

1.00,asthereisnovaliddataorinformationallowingdetermining

itsreliabilityatthenecessarymoment.

Havingexplainedthepreviousfactorsandtheirdeﬁnitions,the

ﬁreriskindex,FRI,rangesfrom0to4,isgivenbyEq.(1)thatdepicts

theratiobetweentheweightedaverageofallthesub-factorsand

thereferenceriskfactor,FRR,on.Thisreferenceriskfactor,FRR,is

determinedtakingintoaccountthetypeofbuildinguse,sincethe

partialfactorrelativetotheﬁreloadnature(PFB5)variesfromcase

tocase,asshowninTable7.

FRI= (1.20×SGI+1.10_FR×SFP+SFE+SFC)/4

R (1)

AsintheARICA originalmethodology,theobtainedﬁre risk

index,FRI,assumestheunitvalueasthereferencevalueforsafety

veriﬁcation.Thus,ontheonehand,aﬁreriskindexvaluehigher

thanthereferencevalue(equalto1.00)suggeststhatfurther

inter-ventionsarerequiredinordertomitigateitsﬁrerisk.Ontheother

hand,aﬁreriskindexvaluelowerthan1.00meansthatthe

build-ingfulﬁlsthePortugueseﬁrecoderequiredminimumconditions,

howeverthereisstillroomfortheimprovementofsomefeatures

[13,15].Finally,thenormalisedﬁreriskvalue,FRI*,wasobtained

throughthenormalisationofthepreviousFRIvalue,between0and

100,simplifyingthevisualinterpretationofthisoutput,particularly

inaGISenvironment.Notethatﬁreriskassessmentisa

determi-nisticbasedapproachasafunctionoftheempiricaldetermination

ofpartialfactors.

3. CasestudyoftheoldcitycentreofSeixal,Portugal

UndertheﬁreriskassessmentoftheoldcitycentreofSeixal,504

oldmasonrybuildingswereevaluated,spreadovera166,000m2

area [16]. Trying to optimise both ﬁeld inspections and data

processingtime,thecasestudyareawasdividedintoﬁvedifferent

zones,accordingtothetypologicalcharacteristicsofthebuildings

(seeFig.2).Withrespecttothesetypologicalcharacteristics,the

buildingstockwasmainlyconstitutedbyrammedearthandpoor

stonemasonryofirregularfabric,howeverinsomecasessimple

brick masonry walls were also found. Horizontal diaphragms

and rooﬁng structure systems are mostly composedby timber

elements, although occasionally, slender reinforced concrete

slabswerefound.Duetodifﬁcultiesencounteredinaccessingthe

interior of all thebuildings and time constraints, two types of

inspectionswithtwodifferentlevelsofdetailweredeﬁned.Thus,

the504buildingsweredividedinto threegroups basedonthe

detailoftheavailableinformation:theﬁrstgroupcomposedof

the99buildingsforwhichitwaspossibletoperformadetailed

inspection,werestudiedbyﬁllingindetailedchecklistsdeveloped

aspartofthescopeofthisresearch.Asisfullydiscussedin[16],

theinspectionanddiagnosischecklistswerestructuredaccording

tothebuildingcriteria, which weredeﬁnedahead oftime in a

hierarchical manner. The second group was composed of 197

buildingsforwhichonlya non-detailedexteriorinspectionwas

possible.Athirdgroupcomposedof208buildingswasnotincluded

in this study due to thebuildings’ construction characteristics

(R.Cbuildings),actualconservationstates(rehabilitated,inruinor

demolished)andcurrentoccupationstate(unoccupied).

4. Resultsanddiscussion

Withtheapplicationofthissimpliﬁedmethodologyintegrated

inaGIStoolenvironment,itwaspossibletoplotaspatial

map-pingofurbanscaleoutputs.TheGISapplicationsoftwareArcGis®

10.2[17]adoptedinthisstudycombinesgeo-referencedgraphical

information,inwhichpolygonsrepresentbuildings,withseveral

featuresand attributes,allowingfor theirdisplay,selection and

search.Althoughthismappingprocessingwasperformedforthe

parishes of Seixal, Arrentela,Amora and Paio Pires, only those

relatedtotheoldcitycentreofSeixalarehereinpresented.

Theﬁrstresultregardsthemappingofthenormalisedﬁrerisk

indexvalues,FRI*(seeFig.3).Thisindicatorallowsinabroadand

spatialmannertoidentifymoreunsafeandcriticalbuildingstock.

Buildingsclassiﬁedasmostvulnerablegenerallycombineagroup

ofthefollowingsituations:derelictandobsoleteelectrical

instal-lations;structuralsafetyproblems;signiﬁcantﬁreloadingdueto

activitiesdevelopedinthosebuildings;lackorinoperabilityofﬁre

detectionmeans,alertandalarmsystems,constrainedoreven

inac-cessibleevacuationroutes.

Firerisk indexvalues under 20,mean that buildingsdo not

presentsigniﬁcantproblems,orcompromiseﬁre risksafety

sit-uations, being satisﬁed in general the ﬁre safety code pillar

requirements. On theotherhand, buildingspresenting ﬁre risk

indexvaluesover40requirethoroughanalysesandthedeﬁnition

ofpreventivemeasurestoimprovetheirsafetyconditions.Finally,

aﬁrerisk indexvaluebetween20and40 meansthatbuildings

donotcomplywithalltheﬁrecoderequirements,being

neces-sarytoadapt and implement furtherimprovingmeasures.It is

worthnotingthat,althoughtheyhavebeendeﬁnedfrom

compar-ativeanalyseswiththeoriginalARICAapproach,thisboundaries

are indicative and therefore they should not be interpreted

rigidly.

InzonesZ1,Z2andZ3,onecanobservethatseveralbuildings

showFRI*valuesover40,whichgenerallypresentcharacteristics

andfeaturesthatpotentiallyaggravateﬁrerisks.Criticalbuildings

wereidentiﬁedandconsideredforFRI*valuesover60,normally

correspondingtocommercialandservicebuildings,whichoften

possessextremelyhighﬁreloadmaterials,exponentially

increas-ing the vulnerability to ﬁre. In zones Z4 and Z5, due to their

predominantandpronouncedresidentialuse,thisscenarioismore

encouraging,withsmallnumberofbuildingsshowingFRI*values

above40.

Withrespecttotheﬁreignitionsub-factorvalues,SFI,whichis

afunctionoffourpartialfactorsfromPFA1toPFA4(seeTable1),itis

possibletogloballypointoutthatthemajorityofthebuildingstock

hasamoderateignitionrisk,beingthesebuildingslessvulnerable

toﬁreevents,sincetheysomehowshowcharacteristicsthatreduce

theriskofﬁreignition.However,asmallnumberofbuildingswere

classiﬁedwithhightoextremelyhighvaluesofﬁreignition

sub-factorvalues,duetotheirfunctiontypeandpredominantmaterial

nature,butalsoduetotheirgasandelectricalinstallations

ren-deringhigherprobabilitiesofﬁreignition.Thisfactwasonlytrue

forzonesZ1,Z2andZ3,correspondingtotheurbanareaswhereas

small-scaledindustryprevails.

Fig.4showsthemappingof theﬁre propagationsub-factor,

SFP,whichdependsinitsdeﬁnition,onﬁvepartialfactors

deter-mination,fromPFB1toPFB5[12].Themajorityofthebuildingstock

wasevaluatedwithlowpropagationrisk,correspondingmainlyto

residentialbuildingswithlowﬁreload.Buildingsclassiﬁedwith

moderatepropagationriskareinmostcasesnon-residential

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Fig.2. Casestudyareaofandzonedelimitation,fromZ1toZ5.

Fig.3.Normalisedﬁrerisk,FRI∗,mappingforzones(a)Z1,Z2,Z3and(b)Z4andZ5.

Fig.4. Fireignitionsub-factor,SFI,mappingforzones(a)Z1,Z2,Z3and(b)Z4andZ5.

withinsufﬁcientlyspacedalignedopenings,increasingtheirﬁre

riskuptoamoderatelevel,withfocusinzonesZ1,Z2andZ3,

cor-respondingtotradeandserviceareas.Nightlyentertainmentareas

ofSeixalalsoshowlowvaluesofﬁreriskpropagation,reﬂecting

theveryfavourableimpactofcompliancewithcoderequirements

andmonitoringmeasuresobligedbyresponsibleentities.Onlytwo

buildingswereevaluatedwithextremelyhighvaluesofﬁrerisk

propagation,whichcorrespondtomixedresidentialand

commer-cialusebuildings,whereasbothstoredmaterialsandcarriedout

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Fig.5. Accessibilitymapforzones(a)Z1,Z2,Z3and(b)Z4andZ5.

Fig.6.Firehydrantsmappingavailableinzones(a)Z1,Z2,Z3and(b)Z4andZ5.

The resultsobtained for the building evacuationsub-factor,

SFE,havedistinguishedcommercialand servicesbuildingswith

the mostunfavourable values in terms of ﬁre risk evacuation.

Although building evacuation can be conducted with more or

less difﬁculty amongst the old building stock, several reasons

canbepointedoutasresponsibleforincreasingevacuationtime.

Excludingthoserelatedwithbehaviouralaspects,whichare

com-prehensivelydiscussedin[18],deﬁcientevacuationescaperoutes

andtheconﬁgurationandefﬁciencyofdetection,alertandalarm

systems,canbepointedoutasthemostsigniﬁcantones.

Externalﬁrefactorsareavitalandconstrainingaspectofthe

firefightinginoldcitycenters,inparticularlythefirehydrant

loca-tionand operabilityandexternalaccessibilityconditions,which

typicallyaredifﬁcultduetonarrowstreetsandsteepslopes.In

zoneZ1,thepresenceofnarrowstreets,oftenobstructedbyillegal

anddisorganisedparking,raisedbythepresenceofurban

equip-ment(benches,busstops,telephonebooths)installedinstrategic

locations,makesthisa problematicissueintermsof

accessibil-ity,affectingtheﬁre combatresponse. Furthermore,inside this

areatherearepedestrianpathways,whichmakescombatusing

ﬁrevehiclespracticallyimpossible.Intheremainingzones,theﬁre

combatresponseingeneralwasclassiﬁedasefﬁcient,although

smallurbanpocketsneedgreaterattention.Intermsofexternal

ﬁrehydrants,theoldcitycentreiswellserved,despitethefactof

notbeingentirelycompliantwiththeﬁresafetycode.

Incaseofanurbanﬁre,theaccessibilityconditionsofcompetent

civilprotectioninstitutions(ﬁrebrigade)areofgreatimportance.

The spatial mapping of partialfactor PFD1, allows plotting out

theextremelyimportantaccessibilityroutingmap(widthofthe

streets,avenuesand alleys),which ispresentedina categorised

manneronFig.5.

Thisaccessibilityroutelayoutwasbasedontwocriteria:clear

widthand height,and slope. Forthe clearwidthand heightof

the street,it wasconsidered as the minimumreference value,

3.5 and 4.0 metersrespectively (values deﬁned in thenational

ﬁre code), taking into account obstacles, foot pathways, urban

equipment.Tocategoriseaccessibilityconditions,threelevelswere

deﬁned:

• inaccessibleorpossiblyblockedwithawidthlowerthan3.5m,

oronlyaccessiblebyfoot(redcoloured);

• partiallyconditionedroutes(yellowcoloured);

• unobstructed routesthat do not offeraccessibilitylimitations

(greencoloured).

Itshouldbenotedthatthismappingisconsideredconservative

andadjustabledependingonthetypeofﬁreﬁghtingvehiclesfor

useinurbanﬁrecombat.

Aimingtoevaluatethestateofconservationandoperabilityof

ﬁrehydrants,netregisterswereassessedbyaddingsome

miss-ingorunregisteredwaterservicehydrantsandverifyingtheexact

locationoftheremainingones.Fromthiseffort,itwaspossibleto

mapSeixal’sactualﬁrehydrantsnetwork(seeFig.6),distinguishing

(7)

Theﬁresafetycodecurrentlyineffectrequires,ontheonehand,

theexistenceofone ﬁrehydrant ata maximumdistanceof 30

metersofeachmainbuildingexit,andontheotherhand,the

exist-enceofonewallhydrantsatevery15metersofwall.Inoldcity

centres,theserequirementsarenotmet.For thisreason,inthis

simpliﬁedmethodology,itwasconsideredreasonabletoextend

theexistenceofﬁrehydrantsatamaximumdistanceof100meters,

independentlyofitstype.Morethantherequirementsintermsof

thenumberofﬁrehydrants,itisfundamentalthatalltheexisting

onesareworkingproperlywithadequatepressureandﬂowrate,

whichwasnotalwaysassured.

5. Conclusions

Asmentionedabove,thevulnerabilitytoﬁreriskinoldurban

areasdependsonvariousfactors,aspresentedasdiscussed

previ-ously.Themethoddevelopedfortheassessmentofurbanﬁrerisk

isbasedonthesimpliﬁedmethodARICAandwasdevelopedfor

large-scaleassessmentandoperationscale,sincetheapplication

ofthementionedoriginalmethodtoallbuildingswithinthearea

studiedisnotpossibleduetotimeconstraintsissuesandtothe

limitedaccessconditionsoftheinteriorofbuildingsoron

consul-tingdrawingsanddetails.

Theresultswerefoundreliable,takingintoaccountthescaleand

aimofthisstudy,allowingtheidentiﬁcationofthemostvulnerable

buildingsinrespecttoﬁrerisk.Fromtheassessmentcarriedout,it

waspossibletoidentifythemainﬁreprotectionandcontrol

meas-uresthatshouldbeimplementedinthenearfuture.Theprincipal

concernsandﬁresafetyneedsforoldcitycentersarediscussed

below.

Electricalandgasinstallationsareoneofthemostcommonﬁre

spreadingcauses.Thelackofinformationisnodoubttheworstof

problem.However,gascontainersstillcontinuetobeconditioned

inclosedunventilatedareas.Electricalcablingisalsoresponsible

forpotentialﬁreignition,withtheabsenceofelectricalbreakers

andoldelectricalinstallationswithoutanytypeofprotection.Inold

citycentresandparticularlyinthepresentcasestudy,theexistence

ofsmallcommercialandserviceareasatthegroundﬂoorlevelare

frequent,whileupperﬂoorsareexclusivelyforresidentialpurposes

(mixeduseofbuildings),inwhichﬁresafetylegalrequirementsare

oftenneglected[15].

InordertoreduceﬁrerisksintheoldcitycentreofSeixal

sev-eralshort and medium term measuresare mentioned, suchas

closesurveillanceofunoccupiedorabandonedbuildings,alerting

ownerstotheconsequencesincaseofaﬁreevent,improvingthe

ﬁrehydrantsnetwork,providingrecognitionmeasuresofbuildings

withcriticalﬁreloads,analysingthemoreadequateﬁrecombat

vehiclefor conditionedaccesslocationsand ﬁredrillsincritical

areaswithintheoldcitycentre.

Theproposedmethodology wasvalidated bycomparingthe

achievedresultswiththoseobtainedapplyingtheoriginalARICA

(in[19])toﬁvebuildingsconsideredtypologicallyrepresentative

ofSeixal’sbuildingstock.Globally,althoughnon-expressive

devia-tionswerefound,theachievedresultsfromthisdirectcomparison

canbeseenaspositiveandsatisfactory,sincemaximumdeviations

werecalculatedin6%.Nonetheless,furthervalidationshouldbe

carriedout,byincreasingthesamplesize,allowingamoredetailed

analysisonthereliabilityoftheproposedmethod.

TheintegrationoftheachievedresultsintoaGIStoolhasagain

provedtobeaveryefﬁcientandusefulstrategyfordatastorage,

namelybuildingfeaturesandsurveyinformation,andalsoforthe

creationofriskscenarios.Thesefeatures,combinedwiththe

pos-sibilityofmappingdifferentoutputs,makeGISaneffectivetoolin

thesupportofmitigationstrategiesandmanagementofﬁreriskat

anurbanscale.

Furtherimprovementsshouldbeimplementedinthepresented

methodology, such as the inﬂuence of adjacent buildings with

higher ﬁrerisk potential,whichshouldnaturally beconsidered

when assessing neighbouring buildings. Moreover, uncertainty

analysisandofthehumanfactorsinorderprovideexposure

param-eterdeﬁnitionandevacuationprocedurecharacterizationshould

be also addressed on further studies. Finally, as the proposed

methodologyisbasedonPortugueseﬁrecodes andregulations,

limitingitsapplicabilitytoothercountries,furtherdevelopments

shouldaddressitsadaptationtoEuropeanﬁrecodesinforce,sothat

itcouldbeapplicableandextendedtootherEuropeancountries.

Acknowledgments

The authors would liketo acknowledgethe Civil Protection

DepartmentofSeixalMunicipalityfortheircontributionand

coop-erationonprovidingadequateandup-to-dateinformationduring

allthebuildinginspectionappraisalandrecordingactivity,aswell

aslogisticsupport.Theanonymousreviewersarealsothankedfor

theirinsightfulcommentsandconstructivesuggestions.

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