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Structural Steel Fire Engineering
ECCS Technical Meeting17-19. September 2008Aalesund, Norway
Louis-Guy CAJOTArcelorMittalResearch & DevelopmentStructural Long Products Esch/Alzette GD-Luxemburg
Structural Steel Fire EngineeringECCS - 18 September 2008 1
Structural fire safety
© Skidmore, Owings & Merrill LLP / dbox Studio
Single storey buildings(f.i. Industrial hall)
multi-storey buildings
Fire safety engineering (Natural fire, behavior of the whole structure, DIFISEK, Secure with steel network, FRACOF
Fire resistance of structure Occupants and firemen safety
single storey buildingsFire resistance of structure Firemen safety
Fire safety engineering (Non progressive collapse, compartmentation, fire walls, …)
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Multi-storey buildingsSteel market share in multi-storey buildings
Weak knowledge from engineers and architects of the actual performances of the steel in case of fire, still mainly assessed through knowledge from fire test on single element.Fire Safety Engineering not yet fully considered
One of the reasons explaining the differences: Fire Safety Approach. The present low market share in continental Europe is more particularly due to :
Market share / Multi-storey buildings
0
10
20
30
40
50
60
70
80
UK SE NL FI FR BE-LU DE ES
%
Pote
ntia
l
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Classical approach amongst “structural fire safety engineering”methods - Eurocodes 1, 3 and 4
standard fire natural fire
classification fire safety eng.
fire safety eng. fire safety eng.
Prescriptive Performance based
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Time [min]0
200
400
600
800
1000
1200
0 30 60
θ [°C]
90 120 180
* does not consider the PRE-FLASHOVER phase* does not depend on FIRE LOAD and VENTILATION
CONDITIONS
ISO ISOISO
ISO ISO
ISO
ISO
ISO
The ISO curve* has to be considered in the WHOLE compartment, even if
the compartment is huge
* never goes DOWN
Classical approach based on ISO-834 heating curve
Structural Steel Fire EngineeringECCS - 18 September 2008 5
Unprotected steel structures for fire resistance ≤ 30minutesR30 unprotected steel structures (Overdesign [S355,S460] ; benefit of the connections)
Classical approach - Quick use of the Eurocodes
ArcelorMittal Belval & DifferdangeUniversity of Liège
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Steel protection for fire resistance > 30 minutes
Additionnal cost of the protection > 40% of the finished steel cost
0
200
400
600
800
1000
0 30 60 90 120time [min]
tem
pera
ture
[°C
]
15’ 30’ 60’ ISO-curveHE180BHD400x382
HE320A 15mm sprayed material
Classical approach based on ISO-834 heating curve
The protection must be optimized and applied where it is really needed.
ArcelorMittal Belval & DifferdangeUniversity of Liège
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standard fire natural fire
classification fire safety eng.
fire safety eng. fire safety eng.
Prescriptive Performance based
The performance based “structural fire safety engineering”approach according to Eurocodes 1, 3 et 4
Fire Safety Engineering + Global Structural Behavior = Fire Development
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Fire Engineering approach
Scientific analysis based on :Fire scenarioPhysical parameters influencing the fire development (fireload, ventilation, active fire fighting measures, …)
Standard curve
More controlled safety and more efficient solutions because better targeted
Temperature
Cooling ….
ISO834 standard fire curve
Ignition - Smouldering
Pre- FlashoverPre- Flashover
Heating
Post- Flashover1000-1200°C
Post- Flashover1000-1200°C
Natural fire curve
Time
FlashoverFlashover
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Fire Engineering approach
Fire safety concept evaluation based on natural fire.Required data for the fire development calculation methods (fire load [MJ/m²], fire spread, rate of heat release [kW/m²]).Definition of model scenario for usual buildings (offices, schools, shops,…).Simulation of the behaviour of the structure submitted to the different fire scenarii and to the static loads.
European research in the field of the fire engineering achieved between 1994 → 2006 allows to develop Fire Engineering approach including :
Existing regulations and standards based on standard fire.Habits and perception of the professionals of construction.Different regulations depending on the countries and even on the regions.Low expertise of engineers, architects in that domain.Lack of training in that domain.No userfriendly calculation tools.
The implementation of the research results met
solved by :The natural fire was introduced in the Eurocodes, particularly Eurocode 1 - Fire Part.The fire engineering has been dealt with in decree and regulations in different european countries .Userfriendly calculation tools were developed (Ozone), and put on the site www.arcelormittal.com/sectionsTrainings were, and are organized (DIFISEK).A network of competent and qualified engineering offices in the field of fire engineering was developed (SECURE with STEEL).
the following difficulties :
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OzoneNatural Fire calculation according to EC1 Fire Part
Structural Steel Fire EngineeringECCS - 18 September 2008 11
θHot
θCold
OzoneNatural Fire calculation according to EC1 Fire Part
Structural Steel Fire EngineeringECCS - 18 September 2008 12
’Fire Safety Engineering’ application to buildingsin G-D of LuxembourgDIssemination of FIre Safety Engineering Knowledge: DIFISEK
RFCS dissemination project
Austria02 oct 08
Belgium22 oct 08 Germany
14 nov 08
Spain12 nov 08
France01 july 08
UK20 sept 08
Czech Rep24 sept 08
Italy03 dec 08
Portugal05 dec 08
Poland28 nov 08
Swedennov 08
Hungary29 oct 08
Romania14 nov 08
Lithuania05 dec 08
Greecenov 08
Slovenia15 oct 08
Estonianov 08Treated topics
Part 1: Thermal & Mechanical ActionsPart 2: Thermal ResponsePart 3: Mechanical Response of
Structures in Fire Part 4: Software for Fire DesignPart 5-1: Worked Examples Part 5-2: Illustration of Completed
Projects
Available tools for further dissemination
All Presentations and Syllabus in PDF for the 5 parts (17 languages)
http://www.difisek.eu/
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SECURE with STEEL in Europe25 European engineering offices specialized in
Fire Engineering assisted by 9 universities and/or research centers
Medical Centre - Eich ; G-D Luxembourg
’Fire Safety Engineering’ applicationto buildings in G-D of Luxembourg
ARUP Fire
Austria - Bernard IngenieureBelgium - Greisch, Technum, Steel Information Centre, Delta, University of LiègeCzech Republic - CTU PragueFrance - Arches-Etudes, E2C Atlantique, Terrell InternationalGermany - Lenz Weber Ingenieure, Schmitt Schtumpf Fruhauf & Partner, BFT
Cognos GmbH, Universität of HannoverItaly - Studio di Ingegneria delle StruttureLuxembourg - Schroeder & AssociésPoland - KeonnPortugal - Tal Projecto, GIPAC, University of AveiroSpain - NB35, Idom, LABEINSweden - Swedish National Testing & Research InstituteSwitzerland - MP Ingénieurs, Borgogno Eggenberger + Partner, ETH ZürichThe Netherlands - DGMR, Hamerlinck Advies bureau, Cauberg-Huygens, DHV BVUnited Kingdom - ARUP Fire, University of Edinburgh
Structural Steel Fire EngineeringECCS - 18 September 2008 14
The “structural fire safety engineering” approachEurocodes 1, 3 et 4
standard fire natural fire
classification fire safety eng.
fire safety eng. fire safety eng.
Prescriptive Performance based
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Test in Cardington (UK)
The structuresurvives
the severenatural fire
(θair > 1200 °C)
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FRACOFFire Resistance Assessment of partially protected Composite Floor
standard fire natural fire
classification fire safety eng.
fire safety eng. fire safety eng.
Prescriptive Performance based
FRACOF
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Design of test specimen
CORNER
Structure grid of a real building
Adopted steel frame for fire test
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Rf = 20 minNakedcentral beams
Protectedsurrounding beams
FRACOF
9m
7m
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ISO-834 Curve
Floor exposed to fire below
Loading condition
Uniform loading through 15 sand bags to simulateDead load: 1,25 kN/m²Imposed load: 5,0 kN/m²
Equivalent uniform load3,87 kN/m² ≈ (1,25 + 0,5 x 5)
Partitions ψ1 Imposed Loads
Weight of each sand bag = 1500 kg
Heating condition
FRACOF
0
200
400
600
800
1000
1200
0 30 60
θ [°C]
90 120 180
t [min]
1110
9451006 1049
842
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FRACOF TEST about 80 people from Authorities
Structural Steel Fire EngineeringECCS - 18 September 2008 21
Test resultsR > 120 minutes
Deformed shape 1040 °C
300 °C
Rebars: 300 °C
0
50
100
150
200
250
300
350
400
450
500
0 90 180 270 360 450 540 630 720 810 900Time [min]
Ver
tical
dis
plac
emen
t [m
m]
45cm
34cm
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Fire resistance of secondary beams calculated as single elements
EC4 Fire partCritical temperature = 608 °CFire resistance = 16’
Fire resistance = 20’SAFIR Simulation
Membrane effect highlighted by an academic exampleD
efle
ctio
n [m
]Time [min]
f
65h
f
-1.2
-1
-0.8
-0.6
-0.4
-0.2
00 20 40 60 80 100 120
Structural Steel Fire EngineeringECCS - 18 September 2008 23
T Mobile HeadquartersHatfield Hertfordshire
School in
Turkey
Fire Safety Concept : protected main beams,unprotected secondary beams
Fire safety engineering is aimed at adopting a rational scientific approach which ensures that fire resistance/protection is provided where it is needed rather than accepting universal provisions which may over or under estimate the level of risk.
Arda School,Izmit, Turkey
Structural Steel Fire EngineeringECCS - 18 September 2008 24
Single storey buildings
High potential of steel in single-storey buildings
Market share / Single-storey buildings
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
UK NL SE FR BE&LU DE FI ES
Structural Steel Fire EngineeringECCS - 18 September 2008 25
Real Fires In Industrial Halls - Charleroi
Masonry façade: outside collapse
Steel Façade: inside collapse
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• First phase - thermal expansion of heated members:
• Second phase - collapse of the heated beam:
Behaviour of structure in fire
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Risk of collapse
Failure modes
– collapse of structure towards outside;– collapse of facades and fire walls towards outside;
Risk of collapse of facade elements towards the outside during the expansion phase
– collapse of an adjacent cold structure – progressive collapse.
Risk of progressive collapse of the load bearing structure
Structural Steel Fire EngineeringECCS - 18 September 2008 28
• Design guide– illustrates possible failure modes of industrial halls– proposes methods to avoid them (calculation of displacement and
tensile forces, recommendation for bracing, fire protection of beams next to fire walls and calculation of required fastening force for façade)
• Software “LUCA”– Calculates maximum displacement and tensile forces
Deliverables
Forces : The force that will be obtained in stage of pull must be used to verify the stability of the cold part (force located in the top of the column).
Displacement : The displacements that will be obtained must be used to verify the stability of the interior and exterior walls (façades and Fire Wall)
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Fire Safety of Industrial Hall
Software
Dissemination seminarsMadrid - 12 Nov
Brussels - 17 and 21 NovParis - Dec
Structural Steel Fire EngineeringECCS - 18 September 2008 30
Fire Safety of Industrial Hall - Fire-break wall
1.
Fire starts 2.
Fire development and fusible connections ensure that the link between wall and heated structure disappears
3.
Fully developed fire and failure of the heated structure.
4.
Decay phase of the fire and no damage at all to the compartment on the other side of the wall.
Fire-Break is a steel fire wall produced and commercialised by ArcelorMittalFrance : AM Distribution France / Europe : AM Dudelange (F. Covella)
Structural Steel Fire EngineeringECCS - 18 September 2008 31
Conclusions
Steel structures demonstrate an actual much higher fire safetythan usually appreciated by most players of construction world
Steel structure
Steel structure
>2h of FR>1000°C
Fire safety engineeringDetailed study → Higher safety
Failure modenon-progressive collapseinward failure
Higher safety of firemenductile predictable failurelarge displacement before failuresafe fire wall