prevention and suppression in large carparks
TRANSCRIPT
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
2
Fire scenario’s in carparks
Possible fire scenario’s in closed carparks?
- Localized fire
- Traveling fire (moving localized fire)
- Compartment fire (post flashover)
3
Fire scenario’s in carparks
Possible fire scenario’s in open carparks?
- Localized fire
- Traveling fire (moving localized fire)
- Compartment fire (post flashover)
4
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)
5
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
6
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)
8
Natural fire concept
Prescriptive rules NL-building code:• Compartimentfire (fully developed post flashover fire)
• Limiting maximum consequences (effect)
Fire engineering:
9
Fuel characteristics
Carfire (1995):• fireload ca. 6700 MJ (10.000 MJ)
• fire duration ca. 40 min.
• mass optical density: 400 m2/kg
10
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)
13
Building characteristics: open carpark
Carpark, 1 level:
• No external separationconstruction(90% open)
• Concrete floors
• Natural firedevelopment
Flashover?
14
Open carpark
16
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?
17
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
20
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)
21
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
25
Local influences
• Steel structure: sensitive to local heating
• Concrete floors: sometimes sensitive to local heating
27
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
30
Performance based approach
Carparks are suitable for a performance based approachbecause of the specific fire scenario’s
31
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
33
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)
35
Thank you
Thank you for your attention and interest.
Suggestions / questions:
www.fellowfse.nl
37