carleton university, 82.583, fire dynamics ii, winter 2003, lecture # 11 1 fire dynamics ii lecture...
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Fire Dynamics IILecture # 11Post-flashover FireJim Mehaffey
82.583
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Post-flashover FireOutline
Ventilation controlled fires
Fuel-surface controlled fires
Model: Hot gas temperature (function of time)
Fire resistance test
Characterizing fire severity
Design for resistance
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Post-flashover Fire
Assumptions- Well-stirred reactor - Th uniform throughout enclosure
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Post-flashover FiresWood Cribs, Pallets & Stacked Furniture
Harmathy (1972) identified two burning regimes for room fires involving wooden cribs: ventilation controlled & fuel-surface controlled
= mass loss rate of fuel (kg s-1)
= ventilation parameter (kg s-1)
=
Af = exposed surface area of fuel (m2)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Post-flashover Fires Involving Wooden Cribs
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Example Calculation of Equivalence RatioPost-flashover Fires Involving Wooden Cribs
Post-flashover fire is ventilation-controlled if
/ Af < 0.63 kg m-2 s-1
Eqn (11-1)
Fuel mass loss rate is
Eqn (11-2)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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What do we know about ventilation-controlled post-flashover fires involving wooden cribs, pallets or stacked furniture?
Fuel mass loss rate is
Eqn (11-2)
Rate of entry of air into room is
Eqn (11-3)
Rate of exit of hot gas from room is
Eqn (11-4)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Ventilation-controlled post-flashover fires involving wooden cribs, pallets or stacked furniture
Equivalence ratio is
~ 0.92 Eqn (11-5)
The rate of heat release of the fire is
Eqn (11-6)
The mass flow rate of soot out of the enclosure is
Eqn (11-7)
(Important for assessment of visibility outside the room)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Ventilation-controlled post-flashover fires involving wooden cribs, pallets or stacked furniture
The mass flow rate of CO out of the enclosure is
Eqn (11-8)
Concentration of CO in hot gas leaving enclosure is
Eqn (11-9)(Important for assessment of toxicity outside the room)(This is a very high and dangerous concentration)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Ventilation-controlled post-flashover fires involving wooden cribs, pallets or stacked furniture
The mass flow rate of CO2 out of the enclosure is
Eqn (11-10)
Concentration of CO2 in hot gas leaving enclosure is
Eqn (11-11)This would cause significant increased CO uptake due to hyperventilation. See slide 3-32 in Fire Dynamics I.
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Ventilation-controlled post-flashover fires involving wooden cribs, pallets or stacked furniture
The mass flow rate of N2 out of the enclosure is
Eqn (11-12)
Concentration of N2 in hot gas leaving enclosure is
Eqn (11-13)On a molar basis, air is 78% N2 and the hot gas is 65% N2. Since molecular wt of N2 is 28, molecular wt of air and the hot gas is close to 28. Therefore, the value 28.95 can be use for air and the hot gas with confidence.
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Fuel-Surface Controlled: Post-flashover Fires
T.Z. Harmathy 1972 // wood cribs (cellulosic)Post-flashover fire is fuel-surface controlled if
/ Af 0.63 kg m-2 s-1
Eqn (11-14)
Fuel mass loss rate is
Eqn (11-15)
G = Quantity of wood in room (kg) = Af / G = specific area of wood (m2 kg-1)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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The Rate of Burning of Fuel-Surface Controlled: Post-flashover Fires
Rate of mass loss / unit surface area of fuel is
Eqn (11-16)
Douglas fir:Assume = 550 kg m-3. Assume 80% converted to volatiles and 20% to charRate of advance of char front:
Vc = 0.85 mm min-1
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Some Comparisons
For massive timbers in standard fire resistance testVc = 0.6 mm min-1 Rate of char advance in wood cribs is (slide 8-36)Vc = 2.2 x 10-6 D-0.6 (m s-1) Sticks of square cross and side D (m)
D (mm) Vc (mm / min) 38 0.94 45 0.85 80 0.60
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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- Specific Area of Wood
For Douglas fir: = 550 kg m-3
Dimensional lumber (4 sides exposed)2x2 (38 mm x 38 mm) = 0.191 m2 kg-12x4 (38 mm x 89 mm) = 0.136 m2 kg-12x12 (38 mm x 286 mm) = 0.108 m2 kg-1
Heavy timber column (4 sides exposed)8x8 (191 mm x 191 mm) = 0.038 m2 kg-1
Plywood (1 side exposed)1/2 = 12.7 mm thick = 0.143 m2 kg-11/4 = 6.4 mm thick = 0.286 m2 kg-1
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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- Specific Area of Wood
Harmathys correlation for fuel-surface controlled burning derived from experimental data for wood cribs
Correlation is likely okay for wood cribs, stacked wood pallets & stacked wood furniture where most surfaces are shielded from radiation from hot upper layer
For such items assume ~ 0.13 m2 kg-1 Eqn (11-17)
Harmathys correlation for fuel-surface controlled burning and ~ 0.13 m2 kg-1 are not appropriate for scenarios involving large exposed wooden surfaces like wall panelling
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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G - Quantity of Fuel (kg)
Quantity of fuel in a room is commonly expressed in terms of a calorifically equivalent quantity of wood
Many surveys have been conducted to determine mass of fuel / floor area
Definition: L = specific fire load (kg m-2)= mass of fuel / floor area
G = L x (floor area) Eqn (11-18)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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L - Specific Fire Load (kg m-2)
L is random variable: mean & standard deviation LHarmathy recommendations (old data)
Assuming L follows a normal distribution
Eqn (11-19)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
Occupancy
(kg m-2 )
(L (kg m-2 )
Dwelling
30.1
4.4
Office
24.8
8.6
School
17.5
5.1
Hospital
25.1
7.8
Hotel
14.6
4.2
_1109767839.unknown
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Duration of a Post-flashover Fire
Assume volatiles released in post-flashover phaseLittle mass loss in pre-flashover phaseDominantly glowing char in decay phase Assume total mass loss during post-flashover phase is MT = 0.8 G (kg) Eqn (11-20) Duration of post-flashover phase is
Eqn (11-21)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Duration of a Post-flashover Fire
For a fuel-surface controlled fire
Eqn (11-22)
For a ventilation controlled fire
Eqn (11-23)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Duration of Post-flashover Fire
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
Test
G
kg
Af
m2
V C
or
F S C
Duration
test
min
Duration
theory
min
1
0.92
130
16.9
0.054
VC
18.5
20.9
2
0.92
130
16.9
0.054
VC
21
20.9
3
0.92
234
30.4
0.030
VC
28
37.7
4
1.42
234
30.4
0.047
VC
24
24.4
5
2.13
234
30.4
0.070
VC?
17
16.5
_1110028394.unknown
_1110028524.unknown
-
Kemano
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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S-987
Chart1
2012.3111.47
0.2092515.0411.74
0.375783333315.7312.45
0.542466666718.2114.08
0.709833333322.2614.76
0.876066666724.7416.5
12426.316.63
1.209366666723.6616.71
1.376483333325.5518.57
1.542716666724.7219.37
1.709833333331.1320.89
1.876216666728.5420.84
22731.9320.46
2.209816666735.2621.69
2.376233333341.4624.03
2.5425556.7628.48
2.709833333382.6334.11
2.8760833333128.3141.26
33119056.56
3.2096166667358.07161.46
3.3760833333458.12319.02
3.5424666667764.53471.01
3.7093833333885.03794.41
3.8758333333853.09793.87
434718.69620.7
4.2094166667662.63567.08
4.3764333333697.9699.13
4.5428333333765.8722.51
4.7091166667749.35856.6
4.87625726.91806.35
538732.64785.88
5.2096666667760.73839.49
5.3762333333725.54794.96
5.5425166667668.39697.06
5.7095833333687.98713.11
5.8758666667732.67808.66
571757.93784.29
6.2094666667738.53734.6
6.3759666667751.46788.84
6.5424833333753.91825.56
6.7095833333739.29761.04
6.87585734.52756.35
604760.12797.28
7.20945780.08785.59
7.3757833333797.58791.54
7.5430333333830.61817.94
7.7095333333840.41829.27
7.8760166667850.01845.02
638907.31894.69
8.2097166667820.4817.83
8.3760833333924.27902.86
8.5426333333966.93943.78
8.7098166667923.15904.69
8.8761166667959.31940.9
671986958.75
9.20956666671004.51975.42
9.37591006.24976.73
9.54246666671015.8984.78
9.70993333331023.46991.88
9.87631666671020.6992.63
7041032.26996.74
10.20941035.58999.31
10.37583333331030.02991.73
10.54311051.571006.35
10.70958333331052.511008.4
10.876051071.241019.46
7151082.451026.24
11.20983333331082.021030.61
11.376151073.521020.54
11.54273333331085.151026.12
11.70931666671083.021027.02
11.87601666671085.41025.87
7261084.891029.37
12.20966666671083.581025.79
12.37606666671095.21035.56
12.54248333331085.261034.39
12.70978333331081.631035.33
12.87626666671081.161040.08
7381083.651042.63
13.20971666671077.761040.5
13.37616666671073.961039.59
13.542451080.221040.04
13.70991080.671041.59
13.87638333331070.531034.59
7491069.831032.71
14.20981666671065.421028.58
14.37643333331072.791028.36
14.542851071.211027.58
14.709451057.561019.48
14.87578333331067.291022.18
7601055.11014.58
15.20968333331039.571003.01
15.37583333331031.47997.06
15.542851028.45991.5
15.70971017.06975.99
15.87651666671008.51975.68
7671009.78980.06
16.20968333331000.48974.8
16.3759999.03969.8
16.5428166667995.43970.1
16.7091166667992.1966.02
16.8761981.81957.5
774981.14955.27
17.2095968.85948.87
17.3763333333962.87943.61
17.5424833333951.98934.99
17.70945944.43928.85
17.8762833333935.85920.47
781929.2915.52
18.2095166667918.27904.91
18.3763333333910.08898.89
18.5424666667903.74892.23
18.70945892.48883.72
18.8765333333880.88870.69
788841.12830.05
19.209633333366.4667.89
19.375866666760.3360.01
19.542583333355.4152.9
19.709566666745.2145.06
19.875933333337.0539.37
79538.1939.74
20.20936666673940.35
20.3764540.0240.11
800.22121
805.42222
810.62323
815.82424
8212525
825.42626
829.82727
834.22828
838.62929
8433030
846.83131
850.63232
854.43333
858.23434
8623535
865.23636
868.43737
871.63838
874.83939
8784040
880.84141
883.64242
886.44343
889.24444
8924545
894.64646
897.24747
899.84848
902.44949
9055050
907.25151
909.45252
911.65353
913.85454
9165555
918.25656
920.45757
922.65858
924.85959
9276060
Living Room Fires - Duplex
ASTM E 119 & CAN/ULC-S101
Time (min)
Temperature (oC)
Fire Exposures
Sheet1
0.020.012.3111.471010.586
0.215.0411.741020.555
0.415.7312.451030.547
0.518.2114.081040.548
0.722.2614.761050.59
0.924.7416.51060.564
1.0124.026.316.631070.59
1.223.6616.711080.562
1.425.5518.571090.589
1.524.7219.371100.563
1.731.1320.891110.59
1.928.5420.841120.573
2.0227.031.9320.461130.553
2.235.2621.691140.589
2.441.4624.031150.574
2.556.7628.481160.553
2.782.6334.111170.59
2.9128.3141.261180.565
3.0331.019056.561190.55
3.2358.07161.461200.577
3.4458.12319.021210.565
3.5764.53471.011220.548
3.7885.03794.411230.563
3.9853.09793.871240.55
4.0434.0718.69620.71250.579
4.2662.63567.081260.565
4.4697.9699.131270.586
4.5765.8722.511280.57
4.7749.35856.61290.547
4.9726.91806.351300.575
5.0538.0732.64785.881310.559
5.2760.73839.491320.58
5.4725.54794.961330.574
5.5668.39697.061340.551
5.7687.98713.111350.575
5.9732.67808.661360.552
6.0571.0757.93784.291370.589
6.2738.53734.61380.568
6.4751.46788.841390.558
6.5753.91825.561400.549
6.7739.29761.041410.575
6.9734.52756.351420.551
7.0604.0760.12797.281430.583
7.2780.08785.591440.567
7.4797.58791.541450.547
7.5830.61817.941460.582
7.7840.41829.271470.572
7.9850.01845.021480.561
8.0638.0907.31894.691490.547
8.2820.4817.831500.583
8.4924.27902.861510.565
8.5966.93943.781520.558
8.7923.15904.691530.589
8.9959.31940.91540.567
9.0671.0986958.751550.55
9.21004.51975.421560.574
9.41006.24976.731570.554
9.51015.8984.781580.548
9.71023.46991.881590.596
9.91020.6992.631600.579
10.0704.01032.26996.741610.582
10.21035.58999.311620.564
10.41030.02991.731630.55
10.51051.571006.351640.586
10.71052.511008.41650.575
10.91071.241019.461660.563
11.0715.01082.451026.241670.554
11.21082.021030.611680.59
11.41073.521020.541690.569
11.51085.151026.121700.564
11.71083.021027.021710.559
11.91085.41025.871720.561
12.0726.01084.891029.371730.549
12.21083.581025.791740.58
12.41095.21035.561750.564
12.51085.261034.391760.549
12.71081.631035.331770.587
12.91081.161040.081780.576
13.0738.01083.651042.631790.568
13.21077.761040.51800.583
13.41073.961039.591810.57
13.51080.221040.041820.547
13.71080.671041.591830.594
13.91070.531034.591840.583
14.0749.01069.831032.711850.579
14.21065.421028.581860.589
14.41072.791028.361870.586
14.51071.211027.581880.571
14.71057.561019.481890.567
14.91067.291022.181900.547
15.0760.01055.11014.581910.55
15.21039.571003.011920.581
15.41031.47997.061930.55
15.51028.45991.51940.571
15.71017.06975.991950.582
15.91008.51975.681960.591
16.0767.01009.78980.061970.561
16.21000.48974.81980.581
16.4999.03969.81990.554
16.5995.43970.12000.569
02016.7992.1966.022010.547
1123.616.9981.81957.52020.566
2227.217.0774.0981.14955.272030.547
3330.817.2968.85948.872040.57
4434.417.4962.87943.612050.58
553817.5951.98934.992060.549
6571.217.7944.43928.852070.567
7604.417.9935.85920.472080.577
8637.618.0781.0929.2915.522090.591
9670.818.2918.27904.912100.571
1070418.4910.08898.892110.58
11715.218.5903.74892.232120.548
12726.418.7892.48883.722130.567
13737.618.9880.88870.692140.592
14748.819.0788.0841.12830.052150.567
1576019.266.4667.892160.578
1676719.460.3360.012170.552
1777419.555.4152.92180.555
1878119.745.2145.062190.574
1978819.937.0539.372200.556
2079520.0795.038.1939.742210.584
21800.220.23940.352220.562
22805.420.440.0240.112230.587
23810.621800.2
24815.822805.4
2582123810.6
26825.424815.8
27829.825821
28834.226825.4
29838.627829.8
3084328834.2
31846.829838.6
32850.630843
33854.431846.8
34858.232850.6
3586233854.4
36865.234858.2
37868.435862
38871.636865.2
39874.837868.4
4087838871.6
41880.839874.8
42883.640878
43886.441880.8
44889.242883.6
4589243886.4
46894.644889.2
47897.245892
48899.846894.6
49902.447897.2
5090548899.8
51907.249902.4
52909.450905
53911.651907.2
54913.852909.4
5591653911.6
56918.254913.8
57920.455916
58922.656918.2
59924.857920.4
6092758922.6
59924.8
60927
Sheet2
Sheet3
Sheet4
-
Time-averaged Temperatures in Room FiresExperimental data from SFPE handbook
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Post-flashover Fires Involving Wood, PMMA & PE
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Burning rate in post-flashover fires involving fuels with exposed surfaces is enhanced by radiationLarge burning rates inhibit inflow of air so increase equivalence ratio reduced heat release (inside)Heat release rate still can be ventilation-controlled
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Traditional Design for Fire Resistance
Basic Objective: Provide sufficient time for escape
Strategy # 1 - Compartmentation: Inhibit fire spread: enclose compartments with fire resistant separations
Strategy # 2 - Structural Fire Protection: Delay collapse of structure: make elements fire resistant
Functional Requirement: Assemblies must perform acceptably when exposed to design fire & design load
Acceptance Criterion (Not clearly stated): Fire separations & structural members must perform intended functions for duration of fire
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Physical Model - Post-flashover Fire
The Fire Resistance Test
Physical (as opposed to mathematical) model of a post-flashover fireInitial development ~ 1908
Standard Fire Resistance Tests
CAN/ULC-S101, Standard methods of fire endurance tests of building construction materialsCAN/ULC-S101 = ASTM E119(Determination of loads is different)ISO 834 = international standard
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Standard Temperature-time Curve: CAN/ULC-S101 or ASTM E119
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Performance RequirementsSeparating Element1. Specimen remains in place2. No passage of hot gas / flame3. T < 140C (average unexposed side)T < 180C (single point, unexposed side)4. Hose-stream Test
Load-bearing Element1. Specimen supports design load
Fire-resistance RatingTime specimen meets performance requirements
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Principle for Establishing Fire Resistance Requirements for Buildings
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Principle for Establishing Fire Resistance Requirements for Buildings
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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NBCC RequirementsCompartmentationFire separations often must be fire ratedFire separations between public corridors & suites in small buildings require fire-resistance rating of 3/4Fire separations between public corridors & suites in large buildings require fire-resistance rating of 1 hour
Structural Fire ProtectionFloors and structural elements supporting floors often must be ratedIn small buildings: fire-resistance rating of 3/4 or 1 hIn large buildings: fire-resistance rating of 2 h
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Performance-based Design for Fire ResistanceDesign Fire Scenarios
Buildings with High Degree of CompartmentationExamples: Apartment & office buildingsScenario: Post-flashover fire (no suppression)Design Fire: A credible but severe post-flashover fire
Buildings with Large Open SpacesExamples: Warehouses & FactoriesScenario: Localized fire (diffusion flame)Design Fire: A credible but severe localized fire
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Model for Post-flashover Fire SeverityJapanese Parametric Model Basic Assumptions
Ventilation: Assume unprotected openings are open Assume fire-rated closures remain intact
Heat Release: Heat released in post-flashover phase Maximum possible value from t=0
Fuel Load: Total fuel load is consumed
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Japanese Parametric Modelfor Ventilation Controlled Fires
Temperature of fire gases: Th(t) (K)
Th(t) - To = t1/6 Eqn (11-24)
where = a constant (K s-1/6) t = time since ignition (s)
Eqn (11-25)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
_1110109404.unknown
-
A = area of openings (windows) (m2)
h = height of openings (windows) (m)
AT = total area of boundaries (m2)
k = thermal conductivity boundaries (kW m-1 K-1)
= density of boundaries (kg m-3)
c = specific heat of boundaries (kJ K-1 kg-1)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Duration of post-flashover fire: tD (s)
Eqn (11-26)
L = fuel load (kg m-2)
AF = area of the floor (m2)
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
_1110109956.unknown
-
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
Japanese Parametric Model
Model Validation
Test
G = L AF
(kg)
Ah
(m5/2)
AT
(m2)
kc
(kJ m-2 s-1/2 K-1)
(K s-1/6)
tD
(s)
1
130
0.92
45.24
0.868
252
1570
2
130
0.92
45.24
0.334
346
1570
3
233
0.92
45.24
0.666
275
2814
4
233
1.42
44.96
0.666
318
1823
5
233
2.13
44.61
0.666
365
1215
-
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Japanese Parametric Model
Option 1: Response of Assembly Predicted Using Mathematical Model
Fire characterized by temperature-time curve generated by Japanese parametric model.
Load carried by structural members taken directly from structural analysis (Part 4 of the NBCC).
A fire-resistance model is used to predict thermal and structural response of each assembly.
Do fire separations and structural members meet the acceptance criteria?
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Japanese Parametric Model
Option 2: Response of Assembly Predicted Using Physical Model
Heat absorbed by unit surface area of fire separations or structural members in post-flashover fire: q (kJ m-2)
Eqn (11-27)
For ISO 834: = 230 K s-1/6 For ASTM E119: = 229 K s-1/6
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
_1110114384.unknown
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Normalized Heat Load Concept(Harmathy & Mehaffey)
Compartment fire of duration tD is equivalent in severity to an ISO 834 fire test of duration teq in which same heat is absorbed per unit area
Eqn (11-28)Assembly fire resistance rating teq is acceptableAdvantage of Option 2: Existing fire resistance ratings can still be usedDrawback of Option 2: Fire-resistance ratings are determined using max load not actual design load
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
_1110114718.unknown
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Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Design ConsiderationsFuel LoadUse 95th percentile in fuel load distribution: Eqn (11-19)VentilationAssume unprotected openings are openAssume fire-rated closures remain intactIf several vents at approximately the same elevation Eqn (11-29)
Compartment BoundariesBoundaries do not include internal partitionsIf there is more than one boundary material
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Example - Design for Fire ResistancePrevent Fire Spread from an Office Suite
Room Dimensions: 6.0 m x 4.0 m x 2.4 m (height)
Floor Area: 6.0 m x 4.0 m = 24 m2
Window Dimensions: 4.0 m x 1.5 m (height)
Fuel Load: 95th percentile Eqn (11-19)
L95 = L + 1.64 L = (24.8 + 1.64 x 8.6) kg m-2 = 38.9 kg m-2
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Ventilation: Window breaks & door remains intact
Compartment boundaries
= [ceiling + walls - vents][gypsum bd] + [floor][n.w. concrete]
= [6x4 + 6x2.4x2 + 4x2.4x2 - 1.5x4] x 0.742 + [6 x 4] x [2.192]
= 101.58 kJ s-1/2 K-1
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
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Japanese Parametric Model
Temperature of fire gases: Th(t) (K)
Th(t) - To = t1/6 Eqn (11-24)
where (K s-1/6) characterises the fire
Eqn (11-25)
\ = 3 x 293 x [ 7.35 / 101.58 ]1/3 = 366 K s-1/6
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
_1110109404.unknown
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Japanese Parametric Model
Duration of post-flashover fire: tD (s)
Eqn (11-26)
\ tD = 38.9 x 24 / [ 0.09 x 7.35 ] = 1411 s = 23.5 min
Duration of equivalent fire resistance test: teq
Eqn (11-28)
\ teq = [366 / 230]3/2 x 23.5 min = 47.2 min
Carleton University, 82.583, Fire Dynamics II, Winter 2003, Lecture # 11
_1110109956.unknown
_1110114718.unknown
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