Post on 11-Jan-2017
Prevention and suppressionin large carparks
Workshop:Projectspecific fire safety concepts forcarparks
Prof. ir. Ruud van Herpen FIFireE
Ruud van Herpen
Nieman consultingengineers:Technical director
Saxion University ofapplied sciences:Professor Fire safety inbuildings
Eindhoven University oftechnology:Fellow Fire Safety Engineering(Dept. Built Environment –Unit BPS)
Closed and open carparks
Definition of an open carpark?
- No external separation constructions
- No roof or ceiling
- No cumulation of smoke safe evacuation
- No cumulation of heatflashover
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Fire scenario’s in carparks
Possible fire scenario’s in closed carparks?
- Localized fire
- Traveling fire (moving localized fire)
- Compartment fire (post flashover)
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Fire scenario’s in carparks
Possible fire scenario’s in open carparks?
- Localized fire
- Traveling fire (moving localized fire)
- Compartment fire (post flashover)
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Thermal load by carpark fires
What fire scenario implicates the most severe thermal loadon constructions?
- Compartment fire (post flashover)
- Traveling fire (moving localized fire)
- Controlled localized fire (manual suppression)
- Controlled localized fire (automatic suppression)
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Public objectives for fire safety
Building act:• Personal safety
• Safety of neighbouring plots
Building code:• Safety of neighbouring plots
• Safety of building (structure) LOD
• Safety of fire/smoke spread (compartments) LOD
• Safety of escape routes
• Safety of attack routes
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Natural fire concept
Natural fire concept:• fire (fuel) building interaction
Two main incidents:• fire start
• flashover
Probability of compartmentfire:
P(bc) = P(fi) x P(f.o.|fi)
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Natural fire concept
Prescriptive rules NL-building code:• Compartimentfire (fully developed post flashover fire)
• Limiting maximum consequences (effect)
Fire engineering:
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Fuel characteristics
Carfire (1995):• fireload ca. 6700 MJ (10.000 MJ)
• fire duration ca. 40 min.
• mass optical density: 400 m2/kg
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Building characteristics: geometry
Carpark, 1 level:− 54 m x 80 m, height 2,5 m
− No wind influences, ambient temperature 20 oC
− No fire suppression (natural fire concept)
− Adiabatic / Inert zonemodel NEN 6055
− Natural ventilation (open carpark) / mechanical exhaust (closed carpark)
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Building characteristics: open carpark
Carpark, 1 level:
• No external separationconstruction(90% open)
• Concrete floors
• Natural firedevelopment
Flashover?
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Open carpark
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Even in an opencarpark the visibilityis poor!(no wind conditions)
Offensive fire attack?
Building characteristics: closed carpark
Carpark, 1 level
• Underground
• Concrete floors andwalls: thermal heavy vsthermal light enclosure
• Mechanical exhaustn = 10 h-1 (30 m3/s)
• Natural firedevelopment
Flashover?
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Consequences of natural fire concept
Pre flashover (open and closed carparks)• Offensive fire attack (suppression):
− Automatic (sprinkler) Localized fire
− Manual (fire brigade: boundary conditions visibility!) Localized fire
• Defensive fire attack (no suppression):
− Creating boundary conditions to prevent flashover Localized traveling fire
Post flashover (closed carparks only)− Fire safety measures according to Building Code
Compartment fire
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Consequences of natural fire concept
Uncertainties:• RHR scenario
− Petrol engines
− Electro engines
− LPG engines
− Hydrogen engines, etc….
• Smoke production
• Homogeneous mixed zones
− Local influences
Robust fire safety concept:• Not very sensitive to uncertainties (stochastic boundary conditions)
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Local influences
Local thermal load on load bearing elements
• Offensive fire attack suppression (automatic or manual):
Thermal load on 1 element (beam, column)
• Defensive fire attack no suppression:
Thermal load on part of load bearing structure(several elements)
Increasing failure probability (no redundancy)
Decreasing acceptable failure probability per element− Probabilistic analysis or
− Applying risk factor on RHR acc. NEN-EN 1991-1-2/NA
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Local influences
• Steel structure: sensitive to local heating
• Concrete floors: sometimes sensitive to local heating
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Boundary conditions
• Concrete building structure
• Acceptable compartment area (building code) = 2,000 m2
• Fire ventilation with capacity 10 h-1 to support offensive fire attack
Assumptions:• Failure probability offensive fire attack = 0.5
• Thermal load compartment fire = 60 min. SFC
• Thermal load traveling fire = 18 min. SFC
• Thermal load localized fire with suppression = 12 min. SFC
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Performance based approach
Carparks are suitable for a performance based approachbecause of the specific fire scenario’s
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SCENARIO'S
characteristics type of fire fire area thermal load prob.
[m2] [min.SFC] [-] [m
2] RF
1 closed compartmentfire 0 0 0 0 0.00
2 not closed (open) traveling fire 430 38 0.5 215 0.11
3 not closed + manual suppression local fire 36 18 0.5 18 0.01
4 not closed + sprinkler small local fire 12 13 0 0 0.00
probabilistic area [m2]: 233
risk factor RF [-]: 0.12
probabilistic thermal load [min.SFC]: 31
probabilistic
Performance based approach
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REQUIRED
fire resistance [min. SFC]: 31 EIW
(residential) 47 R (standard)
63 R (high risk)
Fire/smoke ventilation and automatic alarm to RAC: YES
Automatic sprinkler and sprinkleralarm to RAC: -
REFERENCE (BUILDING CODE)
Max. compartment area (existing buildings) [m2]: 2000
Fire resistance (existing buildings) [min SFC]: 20 EIW
(residential) 30 R (standard)
60 R (high risk)
Fire resistance (new buildings) [min SFC]: 60 EIW
(residential) 90 R (standard)
120 R (high risk)
Performance based fire safetyseparation constructions
Firescenario Barrier Acceptableconvection, conduction, conditions
radiation
(probability of fire) (failure probability) (failure effect)
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