CARLETON Design Fires for Buildings

1DESIGN FIRES FOR COMMERCIAL PREMISES

Dr. Ehab Zalok

Department of Civil and Environmental EngineeringCarleton University

CIB-W014 Fire, Ottawa, 2008 2/24

Background

Codes are moving from traditionally prescriptive building codes towards performance-based codes. Canada: NBC05 and NFC05

Increase in the use of engineering solutions and approaches in the design of fire safety in buildings.

Performance-based designs are done by considering how the building and its fire protection systems perform in the event of a fire.

Building performance is evaluated following a fire hazard analysis procedure.

2CIB-W014 Fire, Ottawa, 2008 3/24

Engineering ApproachPerformancebased Fire Protection

Define project scope

Identify goals

Define stakeholder and design objectives

Develop performance criteria

Develop design fire scenarios

Develop trial designs

Evaluate trial designs

Selected design meets performance criteria?

Select the final design

Prepare design documentation

Performancebased design report

Specification, drawings, and operational and maintenance manual

Modify design or objectives

Develop fire protection engineering design brief

Yes

No

Engineering flowchart of Performancebased Fire Protection SFPE 2000.


Performancebased Fire ProtectionChallenges - Opportunities

Demands a better understanding of the fire hazards of materials and the dynamics of design fires.

Quantitatively measure fundamental properties to evaluate the expected performance of a material, product, or assembly Data could be used with appropriate analytical or computational

models

Require accurate calculations methods to justify the performance to the authority having jurisdiction (AHJ)

Data for the fire properties can be obtained from New or Modified standard test methods Index-based, pass-fail fire test methods (prescriptive-based) Performance (performance-based)


Fire Scenarios and Design Fires

Fire hazard analysis requires the identification of: Fire scenarios that may occur in the building (Qualitative) Design fires that should be considered (Quantitative)

Design fires Fire Resistance Tests

CAN/ULC S101 & ASTM E119 & ISO 834-1

t-squared fires 1

Design fire curves Ignition growth flashover - fully developed - decay

2)( ittHRR =


Process for Developing Design Fires

Identification of design fires Fire loads Type of combustibles Arrangement of combustibles Building characteristics

Quantification of design fires Heat release rate (HRR) Production rate of toxic gases

1. Fire load surveys of real buildings

2. Literature3. Statistics

1. Testing2. Computer modeling


(1) Design Fires ProjectObjectives

Develop appropriate design fires representing fires in commercial buildings.

1. Define fire loads and fuel packages representing the types of combustibles in commercial buildings.

2. Produce experimental data showing the burning characteristics of the fuel packages.

3. Develop input data files to be used in fire models (FDS) to represent the fuel packages in commercial premises.

4. Use the input data files developed in Step 3 to model the burning characteristics in real-size stores.


Research Methods

Assessment of the Fire Load(Fire load survey+literature+Statistics)

Design fuel Packages

Conduct Phase I tests, ISO room Phase I modeling (FDS)

Select fuel Packages for Phase II

Conduct Phase II tests,Post-flashover

Define appropriate design fires(HRR, hot layer temperature, and CO and CO2 production rates)

Phase II modeling (FDS)

Define appropriate input file in FDS to predict fire characteristics in real-size stores

Predict burning characteristics

Predict burning characteristics

No

Yes

No

Yes


Discrete FLD Values and PDF of the Lognormal Distribution

2)ln(21

21)(

=x

ex

xf

= population mean = standard deviation

iciihmkQ =


Mean (), 95th percentile (-)

Combustibles Contribution to the FLD

7 7

47

96

18

8.3

60

4141

59

0

10

20

30

40

50

60

70

80

90

100

Textiles Plastics Wood/Paper Food Misc.

% C

ontr

ibut

ion


Fuel Packages Used in Design Fires for Medium/Large-Scale Tests

Fast FoodShoe storeClothing storeClothing store

BookstoreToy StoreStorage areaComputer store


Fuel Packages Used in Design Fires for Medium/Large-Scale Tests

Each fuel package (1.0 m2) represents the fire load density, method of display, and combustible products in the proportions determined in the survey

% of fire load Test Title ID FLD

(MJ/m2)Textiles Plastics Wood/

paper Rubber/ leather

Food products

Computer store CMP-I 812 3.08 50.6 46.3 0.00 0.00 Storage area SA-I 2320 5.60 31.1 49.1 8.50 5.70 Clothing store CLS-I 661 55.0 6.00 37.0 2.00 0.00 Clothing store CLW-I 661 23.0 1.00 76.0 0.00 0.00 Clothing store CLC-I 661 86.0 2.00 12.0 0.00 0.00 Toy store TOY-I 1223 6.59 18.6 74.8 0.00 0.00 Shoe store SHO-I 4900 1.00 0.00 34.0 65.0 0.00 Bookstore BK-I 5305 0.40 0.00 99.6 0.00 0.00 Fast-food outlet FF-I 881 0.30 19.3 38.9 0.00 41.5


Experimental Set-up


Heat Release per Unit Mass of Oxygen

Constant net amount of heat is released per unit mass of oxygen consumed for complete combustion (Thornton 1917)

Heat released has a value of 13.1 MJ/kg of O2 Organic solids/liquids and gases (Huggett 1980)

Example: hexane (complete combustion):

Oxygen Depletion Method (Janssens 1991)C6H14 + 9.5(O2 + 3.76N2) 6CO2 + 7H2O + 35.72N2

oo&& AOOH

a

OeAO

ACO

CO MMmEEEQ

22

2

2

)1()1(12

1)( +

=


Heat Release Rate (HRR)

0

500

1000

1500

2000

2500

3000

0 600 1200 1800 2400 3000Time (s)

Hea

t Rel

ease

Rat

e (K

W)

BK-IICLC-IICMP-IIFF-IISA-IISHO-IITOY-IISlow t-squaredMedium t-squaredFast t-squared

Heat release data

Test ID Pea

k (k

W)

Tim

e1 (M

in)

Gro

wth

rate

CMP-II 2475 4:10 M-F SA-II 2385 2:45 F CLC-II 2660 3:30 M-F TOY-II 2570 4:15 F SHO-II 2555 4:00 M-F BK-II 2375 2:50 S-M FF-II 2700 6:15 S-M


CO & CO2

CO production rates (mg/kJ) CO2 production rates (mg/kJ)

0

2

4

6

8

10

12

14

0 600 1200 1800 2400 3000Time (s)

CO

Pro

duct

ion

(mg/

kJ)

BK-II CLC-II CMP-II FF-IISA-II SHO-II TOY-II

0

20

40

60

80

100

120

140

0 600 1200 1800 2400 3000Time (s)

CO

2 Pro

duct

ion

(mg/

kJ)

BK-II CLC-II CMP-II FF-IISA-II SHO-II TOY-II

Growth / fuel-controlled flaming conditions (early decay), lowest of all phases.

Ventilation-controlled, highest of all phases. (peak = 2-4 times the average)

Smouldering > growth / fuel-controlled flaming conditions(combustion occurring at low temperature)

Visibility and Tenability limits


Comparisons Between One and Two Packages (Experiments SA-I and SA-II)

0

500

1000

1500

2000

2500

3000

0 600 1200 1800 2400 3000Time (s)

Hea

t Rel

ease

Rat

e (K

W)

SA-II

SA-I

0

2

4

6

8

10

12

14

0 600 1200 1800 2400 3000Time (s)

CO

Pro

duct

ion

(mg/

kJ)

SA-II

SA-I

0

20

40

60

80

100

120

140

0 600 1200 1800 2400 3000Time (s)

CO

2 Pro

duct

ion

(mg/

kJ)

SA-II

SA-I

HRR (KW)

CO2 productionCO production


Modeling Objectives

Develop a simple input data file that generates the same fire characteristics as in Phases I and II, in details:

1. Model the fuel packages(material properties and ideal stoichiometric coefficients)

2. Simulate the burning characteristics of Phase I and II tests (HRR, hot layer temperature, CO and CO2 total production )

3. Assess the simulation capability to predict the burning characteristic of real-size stores

Modeling was conducted using the (CFD) model,Fire Dynamics Simulator (FDS) by (NIST)

10


Modelling & Simulation

Challenges: Grid resolution Material density (kg/m3) Heat of vaporization (kJ/kg) Heat of combustion (kJ/kg) Ignition temperature (C)


Sensitivity Analysis

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 600 1200 1800Time (s)

Hea

t Rel

ease

Rat

e (K

W)

PMMA, original

PMMA, 25% decrease in density

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 600 1200 1800Time (s)

Hea

t Rel

ease

Rat

e (K

W)

PMMA, original

PMMA, 25% decrease in HoV

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 600 1200 1800Time (s)

Hea

t Rel

ease

Rat

e (K

W)

PMMA, original

PMMA, 25% decrease in HC

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 600 1200 1800Time (s)

Hea

t Rel

ease

Rat

e (K

W)

PMMA, original

PMMA, 25% decrease inignition temperature

11


Modeling vs. Experimental Results

0

500

1000

1500

2000

2500

3000

0 600 1200 1800

Time (s)

Heat

Rel

ease

Rat

e (K

W)

FF-IIFDS-IIFF-IFDS-I

Heat release rate (kW)

0

200

400

600

800

1000

1200

0 600 1200 1800Time (s)

TC T

empe

ratu

re @

2.1

-m h

igh

(o C) FF-II

FDS-II

Hot layer temperature (C)


Modelling vs. Experimental Results(Total CO and CO2 produced)

G a s d a t a

T e s t T e s t I D

Tota

l CO

(kg)

Tota

l CO

2 (kg

)

C o m p u t e r s t o r e C M P - I I 6 . 0 9 1 0 9 . 3 0 F D S - I I 6 . 4 5 1 1 2 . 3 0 S t o r a g e a r e a S A -I I 5 . 7 4 2 3 0 . 3 0 F D S - I I 6 . 1 2 2 3 9 . 4 1 C lo t h in g s t o r e C L C - I I 2 . 1 1 1 0 1 . 8 0 F D S - I I 1 . 9 1 1 0 7 . 1 8 T o y s t o r e T O Y -I I 4 . 0 4 1 7 4 . 7 0 F D S - I I 4 . 4 5 1 8 0 . 7 9 S h o e s t o r e S H O - I I 8 . 0 5 3 1 1 . 2 0 F D S - I I 8 . 4 9 3 1 5 . 6 1 B o o k s t o r e B K -I I 6 . 0 1 4 0 9 . 4 0 F D S - I I 6 . 4 0 4 1 5 . 8 0

12


Fire in a 10 x 10 x 2.6-m Storewith two 6 x 2.6-m doors

Modelling and simulation provide a cost-effective mean to examine how the system works


Modeling 10 x 10-m Toy Store

0

200

400

600

800

1000

1200

1400

0 600 1200 1800 2400 3000Time (s)

Hot

laye

r tem

pera

ture

( oC

)

Hot layer temperature (C) Heat release rate (MW)

0

10

20

30

40

50

60

0 600 1200 1800 2400 3000Time (s)

Hea

t rel

ease

rate

(MW

)

Theoretical peak 51.5 (MW)

Temperature ranges from 700 to 1200C in an enclosure during the fully-developed fire (Karlsson and Quintiere,2000)

Absolute peak HRR (MW) oo HA518.1=

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CARLETON Design Fires for Buildings