Prevention and suppression in large carparks

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



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Thermal load by carpark fires

What fire scenario implicates the most severe thermal loadon constructions?



- 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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Cascademodel for LOD’s

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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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Fire characteristics

3 421

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Fire characteristics

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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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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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Closed carpark

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Thermal heavy enclosure

No flashover riskPoor visibility!

Closed carpark

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Thermal light enclosure

Flashover risk!Poor visibility!

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 depends on distance to fire axis

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Local influences: RHR

3 421

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Local influences: gastemperature

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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: RHR (incl. risk factor)

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Local influences

• Steel structure: sensitive to local heating

• Concrete floors: sometimes sensitive to local heating

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Example

Existing carpark:

Review fire safety level

Ruud van Herpen

Plan underground carpark

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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

Thermal load and risk factor

32Source: NEN-research linking Eurocode to Building code


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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


60 R (high risk)

Fire resistance (new buildings) [min SFC]: 60 EIW


120 R (high risk)


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Performance based fire safetyseparation constructions

Firescenario Barrier Acceptableconvection, conduction, conditions

radiation

(probability of fire) (failure probability) (failure effect)

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Performance based fire safetyseparation constructions

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Thank you

Thank you for your attention and interest.

Suggestions / questions:

[email protected]

www.fellowfse.nl

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Prevention and suppression in large carparks

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