Dr. Danny Hopkin CEng 11th April 2017 · DJH_STiFF_110417 Author: David Rush Created Date: 4/24/2017 9:28:00 AM ...

Dr. Danny Hopkin CEng

11th April 2017

• Aresearcher– interestedintheminutiae

• Aconsultant– managingriskanduncertainty• Lessbotheredabouttheminutiae,moreinterestedinthebiggerpicture

Goals

ConstraintsSolutions

Acrackingjob

Credit.N.Butterworth

TargetReliability

TheFiresThe‘FireResistive’Solution

Acrackingjob

TargetReliability

TheFiresThe‘FireResistive’Solution

Doingacrackingjobisabitmoretough

• Safetyinfinitum?• That’snotwhatsocietyexpects• Ifa‘satisfactory’levelofsafetyisouronlygoal,safetyinfinitumisn’tagreatinvestment• Tolerablerisk(andreliability)iscentraltowhat‘we’do

Ourvs.society’slifesafetyexpectation?

Instructuralengineering

Reducethistoanappropriatelevel

Considertheconsequencesoffailure

Definetheacceptableprobabilityoffailure

Formostapplications1.3E-06fora1YRP

In‘fireengineering’

• Reasonable=fulldurationofappropriate fires

• Theappropriatefiresdependupontherisk(likelihood&consequence)

Likelihood&Consequence

In‘fireengineering’(2)

• Absolute-• Areasonableworstcase- subjective• Kirby,et.al.- limitedapplicabilitytomulti-use• EN1990/NFSC– quitegeneralised• LQI– estimationoffatalitiesandawarenessofcosts

• Comparative–• Requiresanunderstandingofwhattheguidancedelivers…

AcceptancecriterioninPBD

Approx.Pf inherentwithinADBFRPeriods

• Probabilisticeventsleadingtoafireinducedstructuralfailure

Credit.R.Van-Coile

ThermalAction Resistance Model

Likelihood

Geometrical

Development

Mech Action

Startingliveload

Timevar.Qk

Perm.Materials

Strength

Temp.Dep

Geometrical

Loading

Resistance

SomeSourcesofUncertainty

ThermalAction Mech Action Resistance Model

Likelihood

Geometrical

Development

Startingliveload

Timevar.Qk

Perm.Materials

Strength

Temp.Dep

Geometrical

Loading

Resistance

SourcesofUncertainty(2)

Some‘simple’enclosures

Metric/Input Office Residential

Area(sq.m) 500 30Height(m) 3.0 2.4Ventilation Area(sq.m) 175 6.0GlazingFraction(-) 0.1– 1.0 0.1– 1.0Linings GYPB GYPB

Elementaffectedbythefireisontheflooroforigin

Noverticalfirespread

OnlyareaofthecompartmentoforigininfluencesPig

Somekeyassumptions

Some‘stochastic’inputs

AspertheNFSC– C.O.V=0.3

AsperPD7974-1

Abestguess….

AfterJ.Stern-Gottfried(mean1,050°C)

Anecdotal– min5mm/s– max20mm/s

• Steelbeamsupportingaconcreteslab• Protectedwithgypsumboard• FLSutilisationcorrespondingtoalimitingtemperatureof620°C• For355MPasteelà 150MPaapplied• TestdifferentprotectionregimesforFR30– FR120• Element/sub-framefailure:

• Utilityratio>1.0• Utility150/kyϴfy

Asimplestructuralelement

Firefragilitycurve- LHS

Utilityvs.fractile foroneFR60protectionsolution

FromfragilitytoPf

Pf,s =0.10

Thestructuralelementisperfect!100%certaintyofload

Results– 500sq.m Office

Pfofanisolatedelement,NOTTHESTRUCTURE

Results– 30sq.m Apartment

Pfofanisolatedelement,NOTTHESTRUCTURE

FireResistance Solution(min) Pf – Office(500sqm) Pf – Apartment(30sqm)

30 1.4E-04 2.2E-0560 1.3E-05 1.9E-0590 3.2E-06 1.2E-05120 1.3E-06 6.8E-06120+Sprinklers 1.3E-07 6.8E-07

Summary&Comparison

PfofanelementwhenaffordeddifferentFRsolutions

Forcomparison– theNFSC(AnnexBWG5)

Forcomparison– EN1990(Ambient)• RC1– 1E-05• RC2– 1E-06• RC3– 1E-07

Potentiallyexcessive?

AWiP….

Transientvariationinreliabilityindex– FR30–500sqm office

Theneedfortwoacceptancecriteria?

• TheinherentlifesafetyPf foranisolatedelementwithinADBhavebeencrudelyestimated• Theyareverysensitivetoareaand,thus,thechoiceofbenchmark• TheorderofmagnitudesnotedarebroadlyconsistentwiththosetentativelyproposedintheNFSC• ThePf valuesgiveameansofestimatingwhatFRisrequiredofelementsinstraightforwardbuildingsfordifferingconsequences&likelihood• FR120+sprinklersà RC3

• TheconceptofformingtwolifesafetyFLS:• Atargetfortheevacuationphase(wherefailureislesstolerable)• Atargetfortheburnoutphase(wherefailuremightbeanacceptableoutcome)• Convergenceofthetwotargetsforhigh-rise

• Furtherwork:• Aproperreliabilityassessment– theadditionalsourcesofuncertainty• AcontinuousdescriptionofthetargetPf asafunctionoflikelihoodandconsequence

• [email protected]

• https://twitter.com/OlssonFireUK

• http://www.olssonfire.com/