Performance-based design for building fire safety ... - Nexus-idrim.net

The 9 th IIASA-DPRI FORUM on Integrated Disaster Risk Management,12 th October 2009 to 16 th October 2009, Kyoto, JapanPerformance-Based dDesignfor Building Fire Safety inHong KongDr. N.K. FongArea of Strength: Fire Safety EngineeringThe Hong Kong Polytechnic UniversityHong Kong, China12th October 20091

★★IntroductionReferences for fire engineering approach– PNAP 204 Guide to Fire Engineering Approach (PracticeNote for Authorized Persons and Registered StructuralEngineers)– SFPE Engineering Guide to Performance-Based FireProtection : analysis and design of buildings★– BS 7974:2001 Application of Fire Safety Engineering (FSE)Principles to the Design of Buildings - Code of PracticeExamplesIDRiM'09 2

Introductionti★★★In Hong Kong, fire safety design in buildings can be based on– prescriptive approach– fire engineering approach.With prescriptive approach, the designer or architect would followthe guidelines laid down in codes of practice, practice notes forauthorized persons, circular letters etc.For most buildings in Hong Kong, the escape routes design stillbased on these codes of practice to obtain the “deem to satisfy”provision.IDRiM'09 3

New projectPBC designfollowing MoE,MoA, FRC codesFSI designfollowing FSIcodeFEADesign revisedYSubmissionto BDSubmissionto FSDDesign revisedYFEA ?NOpportunitiesfor revision ?NApproved ?Approved ?NOpportunitiesfor revision ?YEvaluation byfire consultantNYYNConsidered byFSC, BD Design rejected Design rejectedOpportunitiesfor revision i ?NApproved ?YNDesignrejectedProceed toconstructionProceed toinstallationProcess for Approving Fire Safety Designs(Ref: Chow, Architectural t Science Review, 2005)IDRiM'09 4

The prescriptive codes, basically onMoE CodesMoA CodesFRC CodesFSI Codes may not be sufficient for providing fire safety insome buildings with special designs.IDRiM'09 5

Fire Codes in Hong KongBS5588?MoE CodesMoA CodesFRC CodesFSI CodesLocal Codes: most of them failed to satisfy the prescriptive codes.IDRiM'09 6

Introductionti★In the code of practice for the provision of means ofescape in case of fire, it provides prescribed figuresfor the building designer to determine– the occupant density of the building,– no. of staircases in both sprinklered and non-sprinklered building,– discharge values, travel distance and staircasewidth etc.IDRiM'09 7

Introductionti★★★While in the code of practice pactce for fire resistingst construction, it mainly described the provisions forthe protection of building and escape route usingsuitable non-combustible materials which possess aspecified fire resistance period for differentconstruction element and resisting the action of fire.It also stipulates the– integrity, stability and insulation requirement forthe building elements.It is presumed that design following these codes ofpractice will provide sufficient protection to theoccupants and the building in the case of fire.IDRiM'09 8

Introductionti★ Under the prescriptive approach,designer or engineers will design theescape route based on the requirementstatedinthecodeof practice withoutquestioning the actual performance ofthese escape routes and its interactionwith the occupants and other buildingfeatures.IDRiM'09 9

Introductionti★★★★For buildings with special features such as the HongKong Airport, buildings with ih atrium, the designers /engineers may not be able to provide fire safety designfollowing the requirement prescribed in the codes ofpractice.It is very common for the designers / engineers to adoptthe fire engineering approach / performance-based fireengineering design for such buildings.Under the fire engineering approach / performance-based fire engineering design, there are no standardfigures for the design of escape route, width of staircaseetc.However, certain principles need to be considered whenfire Engineering g approach / performance-based fireengineering design is adoptedIDRiM'09 10

PNAP 204 Guide to Fire EngineeringApproach11

Determine geometry, constructionand use of buildingDesign complies with Codes?(MOE, MOA, FRC)NOIdentifying i non-compliance;Propose alternative/substitutesAnd demonstrate equivalenceDesign Agreed ?Determine fire scenarioNOYESYESEstablish minimum prescriptiveperformance requirements tocomplyEstablish Max. likely no.of occupants, their locations andBehavioural reactionIdentifying certain fire protectionfeaturesCarry out fire engineeringAnalysis rationaleModify fire safety featuresNOAcceptablePerformanceYESAccept DesignIDRiM'09 12Overview ofFire Engineering Design(PNAP 204)

SFPE Engineering Guide toPerformance-Based Fire Protection :analysis and design of buildings13

Performance-Based DesignProcess (SFPE)Extracted from SFPEIDRiM'09 14

Process Flowchart (SFPE)Defining Project ScopeIdentifying GoalsDefining ObjectivesPerformance criteriaFire ProtectionEngineering DesignBriefDesign fire scenariosTrial designsEval. Trial designsModify Design orObjectivesSelected Design MeetsPerformance Criteria?Select Final DesignPerformance BasedDesign ReportPrepare DesignDocumentationSpecifications, Drawings,And operation andMaintenance ManualIDRiM'09 15

BS 7974:2001Application ofFire Safety Engineering i (FSE)Principles to the Design of Buildings- Code of Practice[Originally BS ISO/TR 13387 “Fire Safety Engineering” g (1999)Part 1: Application of Fire Performance Concepts to DesignObjectives]British StandardIDRiM'09 16

BS 7974Application of fire safety engineering principles to the design of buildings -- Code of practicePublished DocumentsPD 7974-0 PD 7974-1Guide to designframework andfire safetyengineeringprocedures• Designapproach• QDR• Comparisonwith criteria• Reporting andpresentation(Sub-system1)Initiationanddevelopmentof fire withinthe enclosureof originExtracted from BS 7974PD 7974-2PD 7974-3PD 7974-4PD 7974-5(Sub-system 2) (Sub-system 3) (Sub-system 4) (Sub-system5)PD 7974-6(Sub-system6)Spread of Structural Detection of Fire service Evacuationsmoke and response and fire and interventiontoxic gases fire spread activation ofwithin and beyond the firebeyond the enclosure of protectionenclosure of origin systemsorigin• Design approach• Acceptance criteria• AnalysisPD 7974-7Probabilisticriskassessment14 44444444444444 24 44444444444444 3• Data• ReferencesIDRiM'09 17

2-Step ProcessExtracted from BS 7974IDRiM'09 18

Procedure for undertaking the QDR★ The following steps should be taken whenconducting the QDR:– Step 1: review the architectural t design of thebuilding– Step 2: establish tblihthe fire safety ft objectives– Step 3:identify fire hazards and possibleconsequences– Step 4: establish trial fire safety designs– Step 5: identify acceptance criteria and methodsof analysis– Step 6: establish fire scenarios for analysisIDRiM'09 19

Components of Step 1: Review the architecturaldesign of the building★★★★a) building characterization– i.e. the layout and geometry of the building, details of the construction, thenature and extent of the loads acting on the structure (e.g. dead loads andimposed loads) and the degree of fire loading presentb) environmental lifl influences– such as wind and snow, which influence fire safety design through theireffect on structural load levels, smoke ventilation systems and the natureof externalflame a eenvelopes issuing from the ewindows of the ebuildingc) occupant characterization– i.e the type of occupancy, the building population and its distribution, thelikelihood of the fire alarm being raised manually, the type of firedetection and alarm systemd) management of fire safety– i.e. the likely extent and nature of management in the building.IDRiM'09 20

Components of Step 5: Identification ofAcceptance Criteria★ Criteria against which the adequacy of adesign can be judged using data determinedby one or more of the following methods:– deterministic (including, when appropriate,safetyfactors);– probabilistic (risk-based);– comparative criteria;– financial criteria.IDRiM'09 21

Components of Step 6 : Establish fire scenariosfor analysis★The characterization of a fire scenario for analysis purposes p shouldinclude a description of the following, where appropriate:– type of fire– internal ventilation conditions– external ventilation i conditionsi– performance of each of the safety measures– type, size and location of the ignition source– distribution and type of fuel– fire load density– fire suppression– state of doors– breakage of windows– building ventilation system.IDRiM'09 22

Components of Step 6 : Establish fire scenariosfor analysis★ Design fires★ To evaluate the effects of a developing fire oneor more design fires on which to base theanalysis should usually be defined.★ A design fire can be characterized in terms of:– heat release rate– toxic species production rate– smoke production rate– fire size (including flame length)– time to key events, e.g. flashoverIDRiM'09 23

Components of Step 6 : Establish fire scenariosfor analysis★A more complete description of a design firemay include one orall of the following phases:– a)incipient phase:❯ characterized by a variety of combustion processes which may besmouldering, flaming or radiant;– b)growth phase:❯ covering the fire propagation period up to flashover (if appropriate) orfull fuel involvement;– c) fully developed phase:❯ characterized by substantially steady burning rates, may occur inventilation or fuel bed controlled fires;– d) decay phase:❯ covering the period of declining fire severity;– e)extinction:❯ when there is no more energy being released.IDRiM'09 24

Quantitative Analysis★ To simplify the evaluation of the fire safetydesign, the fire safety engineering processshould be further broken down into six subsystems(SS).★ The sub-systems can be used individually toaddress specific issues or together to address allof the main aspects of fire safety.IDRiM'09 25

Quantitative Analysis★The sub-systems are as follows:– Sub-system 1:❯ initiation and development of fire within enclosure of origin (PD7974-1)– Sub-system 2:❯ spread of smoke and toxic gases within and beyond enclosure oforigin (PD 7974-2)– Sub-system 3:❯ structural response and fire spread beyond enclosure of origin(PD 7974-3)– Sub-system 4:❯ detection and activation of fire protection systems (PD 7974-4)– Sub-system 5:❯ fire service intervention (PD 7974-5)– Sub-system 6:❯ evacuation (PD 7974-6)IDRiM'09 26

SS1: Initiation and development of fire within theenclosure of origin (see PD 7974-1)★ SS1– provides guidance on evaluating fire growthand/or size within the enclosure taking intoaccount the four main stages of firedevelopment:❯ pre-flashover (including early growth anddevelopment);❯ flashover;❯ fully developed fire (where all the fuel isburning);❯ decay.IDRiM'09 27

SS1: Initiation and development of fire within theenclosure of origin (see PD 7974-1)★ Given the information in PD 7974-0, it is thenpossible to calculate a number of parameters,which include:– heat release rate;–massproduction rate of smoke;– mass production rate of fire effluents (e.g. CO);– flame size and temperature;– temperature within enclosure;– time to flashover;– area of fire involvement.IDRiM'09 28

SS1: Design fires★★Following identification of the design fire scenarios, it is necessaryto describe the assumed characteristics of the fire on which thescenario quantification will be based.– These assumed fire characteristics are referred to as “the design fire”.The design fire– needs to be appropriate to the objectives of the fire safety engineering task.– For example, if the objective is to evaluate the smoke control system, adesign fire should be selected that challenges the system.IDRiM'09 29

SS1: Design fires★ Design fire– unlikely to occur in practice.★ Actual fires– likely to be less severe and will not necessaryfollow the specified design curve, such as aparticular heat release curve.★ The design fire quantification process–should result in a design profile that isconservative.IDRiM'09 30

Pre-flashover design fires★ t 2 fires★ Smouldering fires★ Burning objects★ Prescribed firesIDRiM'09 31

SS1: InputQDR Sub-system 3 Sub-system 4 Sub-system 5EnvironmentalinfluencesTime of firespread fromenclosureTime toactivation ofsmoke controlTime of fireServiceinterventionDesign fireBuildingcharacteristicsTime tostructuralt failureTime toactivation ofsmoke andfireFire fightingcapabilityTime toactivation ofsuppressionSub-system 1IDRiM'09 32

SS1: outputSub-system 1Heat releaseTime toRate of smokeRate of COFlame sizeFlamerateflashover production productionradiationSub-system 2 Sub-system 3 Sub-system 2 Sub-system 2 Sub-system 2 Sub-system 2Sub-system 3 Sub-system 5 Sub-system 4 Sub-system 5 Sub-system 3 Sub-system 4Sub-system 6 Sub-system 4 Sub-system 5Sub-system 6 Sub-system 6IDRiM'09 33

SS2: Spread of smoke and toxic gases within andbeyond the enclosure of origin (see PD 7974-2)★SS2 provides guidance by which the following maybe evaluated:– the spread of smoke and toxic gases within andbeyond the enclosure of fire origin;– the characteristics of the smoke and the toxicgases at the location of interest.IDRiM'09 34

SS2: analysis ofsmoke andtoxic gasesExtracted from BS 7974IDRiM'09 35

SS3: Structural response and fire spread beyondthe enclosure of origin (see PD 7974-3)★SS3 provides guidance so that the following can beevaluated:– the fire severity❯ in terms of temperature and heat flux within the enclosure;and– the ability of the elements forming the enclosure,directly or in part, to withstand exposure to theprevailing fire severity.IDRiM'09 36

SS3: Structural responseseand fire spread beyondthe enclosure of origin(see PD 7974-3)Extracted from BS 7974IDRiM'09 37

SS3: Structural response and fire spread beyondthe enclosure of origin (see PD 7974-3)Example:Extracted from BS 7974IDRiM'09 38

SS3: Structural responseand fire spread beyondthe enclosure of origin(see PD 7974-3)Extracted from BS 7974IDRiM'09 39

SS4: Detection of fire and activation of fireprotection systems (see PD 7974-4)★SS4 gives guidance on the calculation of thefollowing with respect to time:– detection of the fire– activation of the alarm and fire protectionsystems, e.g. sprinklers, smoke venting systems,roller shutters, etc.– fire service notification.IDRiM'09 40

SS4: Detection of fire and activation of fireprotection systems (see PD 7974-4)★ Determination i of objectives★ Required time to response★ Location and extent of detection★ Type of dt detectionti★ Siting and spacing★ Calculated time to responseIDRiM'09 41

SS4: Detection of fire and activation offire protection systems (see PD 7974-4)★★Fire Control and Warning Systems– Determine the type and extent of local and remote fire warning systemsand the likelyl response times of persons within ihi the premises and firefighting personnel.– Fire suppression systems– Fire barrier systems– Smoke control systemsReview– A thoroughh review of each of thesystemst should now beundertaken to:– — ensure that the systems meet with the requirements of the fire safetyengineering design;– — ensure that the systems function together as designed and that there areno adverse aspects created by the mutual interaction of any of the systems.IDRiM'09 42

SS5: Fire service intervention (see PD 7974-5)★SS5 provides guidance on the evaluation of the rateof build up of fire extinguishing resources of thefire service, including the activities of in-house orprivate fire brigades and in particular:–the time interval between the call to the fireservice and the arrival of the fire service pre-determined attendance–thetime interval between the arrival of the fireservice and the initiation of attack on the fire bythe fire service–thetime intervals related to the build up of anynecessary additional fire service resources– the extent of firefighting resources andextinguishing i capability available at varioustimesIDRiM'09 43

SS6: Evacuation (see PD 7974-6)★SS6 provides guidance on how to assess theresponse of people to fire, including theirevacuation time from any space inside a building.– Criteria for acceptance are contained in this sub-system.★ NOTE 1 The various parts of PD 7974 (PD 7974-1to -6 respectively) for these sub-systems giveselected data and engineering relationships(including information on their applicability) thattmay be used for design.★ This code of practice recognizes the use ofalternative informationIDRiM'09 44

Time line approachIDRiM'09 45

The time line approach★ ASET > RSET– ASET (available safe egress time) is the lengthof time available before untenable conditions arereached and might be defined in terms of:❯ a) the smoke layer height descending to within 2.0 m offloor level; and❯ b) the visibility distance falling below 10 m; or❯ c) the smoke layer temperature exceeding 200 C .– The untenable conditions vary among differentstandards– ASET can be estimated from using modelsIDRiM'09 46

TimeAvailable safe egress time (ASET)The time line comparison between fire development andevacuation/damage to propertyIDRiM'09 47

Required Safe Escape Timedetalarm( Δt Δt )RSET = Δt + Δt + +where★★Δt detpreis the time from ignition to detection which is determinedΔtfrom empirical model such Alpert’s correlation, alarmis the timefrom detection to a general alarmΔt preis the pre-movement time for the building occupants andΔt trav★ the is the travel time of the building occupants which isdt determined dfrom the evacuation software such as SIMULEX,STEPS.travIDRiM'09 48

★★★★Based on above formula, it is apparent that a great delay in initiatingevacuation (i.e. large value of Δt pre ) would lead to a considerablevulnerability of the occupants.Behavioral response of the occupants is one of the important factorsaffecting the evacuation time in the case of fire and would be dictatedby their physical and psychological states at the time of fire awareness,e.g. whether they were asleep, just awake and not dressed, or dressedand awake, the severity of threat posed by fire, the building designand the fire protection devices installed.The reaction of occupants after the perception of fire would beaffected by their perception of the seriousness of the fire.Before egress, many people tend to take preservative action, e.g.collecting important/valuable items.IDRiM'09 49

Δt pre★ In estimating , the cognitive functioning ability of the occupantsis very important.Some people p would treat the audible fire alarmsound as a warning and wait for further information, e.g. notified byneighbor, clarified with management personnel via phone calls beforestarting to evacuate.★Therefore, using this fire engineering approach for escape routedesign, it is important to understand the behavior of the occupants inthe case of fire emergency such that Δt precan be determined andincluded in egress time calculations.Δt pre★ However, the value of varied with considerable uncertainty andit is important t to obtain accurate information of occupants.Δt pre★ The determination of always leads to vigorous argumentsbetween the designers/engineers g and the authority.IDRiM'09 50

★ Physical conditions, occupant distribution,gender, age etc. are very important t inputparameters for the estimation of Δt trav .★ However, in the existing fire engineeringapproach design, no universal guideline wasdeveloped in the determination of these inputparameters.★This again leads to arguments between thedesigners/engineers and the approving authority.IDRiM'09 51

Application Examples52

Example4.6 m16.21 m73.51m1.78mIDRiM'09 53

Eitt Exit to Staircase Sti =1.5 15mStaircaseAssumed blockedby the smokeAssume 3 peoplein each compartmenttCharacteristics defined by Simulex:Case 1: All elderlyCase 2: All male with walking speed=0.5m/smovieIDRiM'09 54

Evacuation profileNo. of people passing th heexit9080706050403020100-10100 sec 135 sec0 50 100 150all maleelderlyTime (sec)The evacuation profile of two different occupant characteristicsiIDRiM'09 55

éééééééOnly 1 typical floor with one 1.5 meter wide exit is considered inthe simulation. Total number of occupants inside the floor is 78.The simulation setup is shown in figure. During the simulation, theresponse time of the occupants is based on random distributionwith mean value equal to 1 min/s.Two occupant types are considered.é elderly typeé all male with 0.5 m/s.For elderly type, the total evacuation time is ~100 sec.For all male with 0.5 m/s, the total evacuation time is 135 sec.This shows that by simply change the occupant type, the simulatedevacuation time is increased by 35 %.A cumulative frequency curve is shown to illustrated the timerequired for the occupants to pass through the exit in floor 1.IDRiM'09 56

Untenable conditions★★★The untenable uteabeconditions o might gtbe determined ed by the tesmoke layer clear height, thermal radiation from fire andenclosure temperature.The time from ignitioni i to the occurrenceof untenableconditions will be estimated and taken to be theavailable safe egress time (ASET) for the buildingoccupants.For example, from PD7974-6:2004 of BS7974, theproposed tenability limits for smoke is Dm -1 =0.0808(visibility 10m).★ Other proposed tenability limits are 2.5kWm -2 forexposure to radiant heat, 115 o C for up to 5 minutesexposure to convected heat etc.IDRiM'09 57

Estimation of the Fire Scenario★★★★★★For this exampleFDS is used to simulate the fire and smoke spreadwithin this floorA typical floor layout is used for the simulation ofthe fire scenarios as shown in the figure.200 x 40 x 6 (i.e. 48000) grid cells are used toperform the calculation.A fire size of 2 MW is used in one of thecompartments for simulations.All the compartment walls are assumed 4 m highand assumed all doors are opened.IDRiM'09 58

Simulation layoutMonitoring point(temperature, visibility,CO concentration)Fire source(2 MW)Staircase used for exitIDRiM'09 59

Smoke spread at 30 secondIDRiM'09 60

Smoke spread at 80 secondIDRiM'09 61

Smoke spread at 160 secondIDRiM'09 62

Temperature distribution near the fire source at 160 secondIDRiM'09 63

movieTemperature distribution along the escape route at 160 secondIDRiM'09 64

Temperature profile at different timeof the mon nitoringpoint (m)32.521.51Temperature profile at50 secTemperature profile at100 secTemperature profile at150 secHeight0.500 100 200 300Temperature profile at200 secTemperature (deg C)Temperature profile near the fire room at different timeIDRiM'09 65

Temperature ProfileTemperature distribution at x=5 mTemperature distribution at x = 10 mHe eight (m)3.002.502.001.50100 1.000.500.000.00 50.00 100.00 150.00 200.00 250.00Temperature (deg C)100 sec200 sec300 sec400 secHe eight (m)3.002.502.001.50500 sec100 1.00600 sec0.50Series70.000.00 50.00 100.00 150.00 200.00Temperature (deg C)100 sec200 sec300 sec400 sec500 sec600 secTemperature distribution at x=15 mTemperature distribution at x = 20 mHeight (m)3.002.502.001.501.000.500.000.00 20.00 40.00 60.00 80.00 100.00 120.00Temperature (deg C)3.00100 sec2.50200 sec2.00Height (m)300 sec400 sec500 sec600 secSeries71.501.000.500.000.00 20.00 40.00 60.00 80.00 100.00 120.00Temperature (deg C)100 sec200 sec300 sec400 sec500 sec600 secSeries7IDRiM'09 66

CO concentration ti profileCarbon Monoxide profile at x= 5mCarbon Monoxide profile at x = 10mHe eight (m)3.002.502.001.50100 1.000.500.000.00 100.00 200.00 300.00 400.00CO concentration (ppm)100 sec200 sec300 secHe eight (m)3.002.502.001.50400 sec100 1.00500 sec0.50600 sec0.00Series70.00 50.00 100.00 150.00 200.00CO concentration (ppm)100 sec200 sec300 sec400 sec500 sec600 secSeries7Carbon Monoxide profile at x = 15mCarbon Monoxide profile at x = 20 mHeight (m)3.002.502.001.501.000.500.000.00 50.00 100.00 150.00 200.00CO concentration (ppm)3.00100 sec2.50200 sec2.00Height (m)300 sec400 sec500 sec600 secSeries71.501.000.500.000.00 50.00 100.00 150.00 200.00CO concentration (ppm)100 sec200 sec300 sec400 sec500 sec600 secSeries7IDRiM'09 67

Thermal RadiationThermal radiation at x=5 mThermal radiation at x = 10mHe eight (m)3.002.502.001.50100 1.000.500.000.00 5.00 10.00 15.00 20.00 25.00radiant intensity (kW/m^2)100 sec200 sec300 secHe eight (m)3.002.502.001.50400 sec100 1.00500 sec0.50600 sec0.00Series70.00 5.00 10.00 15.00radiant intensity (kW/m^2)100 sec200 sec300 sec400 sec500 sec600 secSeries7Thermal radiation at x = 15 mThermal radiation at x = 20 mHeight (m)3.002.502.001.501.000.500.000.00 1.00 2.00 3.00 4.00 5.00 6.00radiant intensity (kW/m^2)3.00100 sec2.50200 sec2.00Height (m)300 sec400 sec500 sec600 secSeries71.501.000.500.000.00 1.00 2.00 3.00 4.00radiant intensity (kW/m^2)100 sec200 sec300 sec400 sec500 sec600 secSeries7IDRiM'09 68

Other examples69

moviestaircase192 x 180 x 6 grid cells(fire size = 2MW)staircaseIDRiM'09 70

moviestaircaseFire size = 2MW192 x 180 x 8 grid cellsstaircaseIDRiM'09 71

Assessment and verification i of model– Verification– Review of the theoretical basis of the model– Comparison with other programmes– Empirical verification– Code checking– Numerical accuracy– Sensitivity analysis❯ E.g. Identify dominant variables in the model❯ Define acceptable range of values for each input variable❯ Demonstrate sensitivity of output variables to variations in input dataIDRiM'09 72

Conclusion★★Fire engineering approach / performance-basedfire engineering design can help us to improve thefire safety design of the buildings.Care must taken to specify the input parameters,building characteristics, occupants characteristics,fire size, boundary conditions, models etc.★For a good fire safety design, factors such ashuman behaviour, future modification, fire safetymanagement etc, should also be considered.IDRiM'09 73

Thank you !74