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Frontiers of Structural and Civil Engineering

ISSN 2095-2430

ISSN 2095-2449(Online)

CN 10-1023/X

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Front. Struct. Civ. Eng.    2014, Vol. 8 Issue (4) : 427-447    https://doi.org/10.1007/s11709-014-0279-1
RESEARCH ARTICLE
Development of realistic design fire time-temperature curves for the testing of cold-formed steel wall systems
Anthony Deloge ARIYANAYAGAM,Mahen MAHENDRAN()
School of Civil Engineering and the Built Environment, Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4000, Australia
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Abstract

Fire resistance rating of light gauge steel frame (LSF) wall systems is obtained from fire tests based on the standard fire time-temperature curve. However, fire severity has increased in modern buildings due to higher fuel loads as a result of modern furniture and light weight constructions that make use of thermoplastics materials, synthetic foams and fabrics. Some of these materials are high in calorific values and increase both the spread of fire growth and heat release rate, thus increasing the fire severity beyond that of the standard fire curve. Further, the standard fire curve does not include a decay phase that is present in natural fires. Despite the increasing usage of LSF walls, their behavior in real building fires is not fully understood. This paper presents the details of a research study aimed at developing realistic design fire curves for use in the fire tests of LSF walls. It includes a review of the characteristics of building fires, previously developed fire time-temperature curves, computer models and available parametric equations. The paper highlights that real building fire time-temperature curves depend on the fuel load representing the combustible building contents, ventilation openings and thermal properties of wall lining materials, and provides suitable values of many required parameters including fuel loads in residential buildings. Finally, realistic design fire time-temperature curves simulating the fire conditions in modern residential buildings are proposed for the testing of LSF walls.
Keywords fire safety      standard fire curve      realistic design fire time-temperature curves      light gauge steel frame (LSF) walls      fire resistance rating      fuel load     
Corresponding Author(s): Mahen MAHENDRAN   
Online First Date: 11 December 2014    Issue Date: 12 January 2015
 Cite this article:   
Anthony Deloge ARIYANAYAGAM,Mahen MAHENDRAN. Development of realistic design fire time-temperature curves for the testing of cold-formed steel wall systems[J]. Front. Struct. Civ. Eng., 2014, 8(4): 427-447.
 URL:  
https://academic.hep.com.cn/fsce/EN/10.1007/s11709-014-0279-1
https://academic.hep.com.cn/fsce/EN/Y2014/V8/I4/427
Fig.1  Stages of development of a fire [3]
Room percent weight (kg) percent fire load (MJ)
W P T W P T
Kitchen 86.5 13.5 <<1% 80.2 19.8 <<1%
living room 65.8 32.9 1.4 57.4 41.4 1.2
dining room 72.6 26.6 0.8 65.0 34.0 0.8
primary bedroom 42.3 26.4 31.4 37.8 34.1 28.1
secondary bedroom 39.8 29.8 30.3 35.2 38.0 26.8
basement living room 61.0 39.0 0.2 51.8 48.1 0.2
Tab.1  Composition of combustible contents in residential dwellings [9]
Fig.2  Standard time-temperature curves [1,11]
Fig.3  Experimental time-temperature curves [12]
Fig.4  Swedish time-temperature curves [16]
Fig.5  BFD curve fitted to a time-shifted Eurocode parametric curve [21]
Fig.6  Eurocode parametric curves for different fuel load density, opening factors and thermal inertia values. (a) Varying fuel load density values; (b) varying opening factors; (c) varying thermal inertia
description test 1 test 2 test 3 test 4 test 5 test 6 test 7 test 8
fire loadtype W W WP W WP W WP WP
lining I HI HI HI HI I I I
opening F F F FB FB FB FB F
max.temperature (°C) 1109 1291 1350 1353 1347 1332 1343 1329
Tab.2  Cardington test data and maximum temperature [4]
Fig.7  Comparison of standard fire with compartment fires [5]
Fig.8  Experimental results of cardington tests showing the minimum, average and maximum temperatures compared with standard fire curve [23]
Description number of samples fuel load density (MJ/m2)
mean standard deviation
2 storey town home 58 490 240
3 storey town home 14 370 240
2 storey detached 231 390 160
3 storey detached 28 390 240
bungalow 118 410 270
apartment 64 440 272
Tab.3  Variable fuel load densities for various family dwellings and rooms in Canadian family dwellings
description fuel load density (MJ/m2)
mean standard deviation
kitchen 807 123
secondary bedroom 594 146
primary bedroom 534 125
living room 412 127
dining room 393 132
basement living room 288 96
Tab.4  
Fig.9  Summary of mean variable fuel load density values-residential buildings
description cold-formed steel [30] rock fiber [29] concrete [12]
density (kg/m3) 7850.00 100.00 2300.00
specific heat (J/kgK) 439.80 840.00 980.00
thermal conductivity (W/mK) 53.33 0.25 1.60
thermal Inertia (J/m2s1/2K) 13569 145 1899
Tab.5  Thermal inertia of fire compartment lining materials
compartment geometry
description L 3.60 3.60
W 2.40 2.40
H 2.40 2.40
total surface area At (m2) 46.08 46.08
EU-1 EU-2 EU-3 EU-4 EU-5 EU-6 EU-7 EU-8
ventilation opening dimensions
door
h1(m) 2.10 2.10 2.10 2.10 - - - -
w1 (m) 0.90 0.90 0.90 0.90 - - - -
Nos 2 1 1 1 - - - -
window
h2(m) 1.20 1.20 1.20 1.20 0.90 0.90 0.90 1.20
w2 (m) 0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80
Nos 4 3 2 1 4 3 2 1
total area of ventilationAv (m2) 7.62 4.77 3.81 2.85 2.88 2.16 1.44 0.96
opening percentage(Av/At) % 16.54% 10.35% 8.27% 6.18% 6.25% 4.69% 3.13% 2.08%
heq (m) 1.50 1.43 1.50 1.65 0.90 0.90 0.90 1.20
opening factor (m2) 0.20 0.12 0.10 0.08 0.06 0.04 0.03 0.02
Tab.6  Calculation of opening factors based on Eurocode [11]
description EU-1 EU-2 EU-3 EU-4 EU-5 EU-6 EU-7 EU-8
opening factor (m1/2) 0.20 0.12 0.10 0.08 0.06 0.04 0.03 0.02
Area of ventilation (m2) 7.62 4.77 3.81 2.85 2.88 2.16 1.44 0.96
compartment thermal inertia (b) (J/m2s1/2K) 749 724 719 715 710 706 702 700
Tab.7  Thermal inertia values for different opening factors- Compartment A
Fig.10  Eurocode parametric time-temperature curves ? Compartment A
Fig.11  BFD and Eurocode parametric time-temperature curves-Compartment A
description ventilation factor (m1/2)
0.03 0.08
from Table 5
total surface area (m2) 46.08 46.08
weighted average of opening height – heq (m) 0.90 1.65
total area of ventilation (m2) 1.44 2.85
critical heat release rate – From Eq. (42) (MW) 0.876 1.743
fire growth rate [13] medium fast
growth constant – k [13] 300 150
time to flashover – from Eq. (4) (mins) 4.68 4.36
Tab.8  Calculation of time to flashover based on heat release rate
Fig.12  Modified BFD and Eurocode parametric time-temperature curves-Compartment A
Fig.13  Modified BFD curves with pre-flashover time shift-Compartment A
Fig.14  Flashover point identification for the modified BFD curves-Compartment A
Fig.15  Realistic design fire time-temperature curves-Compartment A
Fig.16  Wall and ceiling configuration-Compartment B
Fig.17  BFD and Eurocode parametric time-temperature curves-Compartment B
Fig.18  Realistic design fire time-temperature curves-Compartment B. (a) Max temperature modification; (b) pre-flashover time shift modification; (c) EU and modified “BFD” fire curves – Compartment B
Fig.19  Realistic design fire time-temperature curves for use in fire tests
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