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Lezione Sicurezza Strutturale Antincendio Costruzioni Metalliche 17 oct 2013
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Transcript of Lezione Sicurezza Strutturale Antincendio Costruzioni Metalliche 17 oct 2013
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of Denmark
FIRE SAFETY AT DTU‐BYG
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
DTU‐BYG
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
DTU‐BYG
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
FIRE GROUP AT DTU‐BYG
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
FIRE GROUP AT DTU‐BYG
Luisa GiulianiAssistant Professor
Structural fire safety
Anne DederichsAssociate Professor
Toxicity and evacuation
Aldis LarusdottirPh.D. student
Evacuation of children
Grunde JomaasAssociate Professor
Flame spread
Kristian HertzFull Professor
Fire Safety Design, Concrete Structures
Annemarie PoulsenExternal lector
Design fire and regulation
Ludmilla RozanovaPost Doc
Evacuation
Annemarie PoulsenPh.D. student
Evacuation of disabled people
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
Group competences
KHZ AND GRUJO ALLARAMPLUGI JAGS
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
Civil Engineering education (M.Sc.):11020 Building Fire Safety11022 Fire Dynamics11023 Structural Fire Safety
FIRE SAFETY EDUCATION AT DTU
11020 Building Fire Safety
11022 Fire Dynamics
11023 Structural Fire Safety
Special courses
Thesis projects
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
1. Structural fire safety of car parks
2. Thermal resistance of intumescent paints
PERSPECTIVE EXCHANGE STUDENT
3. Fire induced collapse of steel structures
4. Effect of SSI on ship collision with OWT
Available thesis projects on steel structures
DTU SAPIENZA ‐ ERASMUS PROGRAM 2014/15
FIRE SAFETY EDUCATION AT DTU
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
0. Semester – Efterår 201011E16 Ingeniørmæssig matematik og
fysik for Bygningskonstruktører
1. Semester – Forår 201111B12 Brandmodellering 1 11B01 Konstruktionsbrandteknik 11B11 Miljøkemi
2. Semester – Efterår 201111B25 Branddynamik 11B04 Brandkemi11B24 Bygningsbrandteknik
3. Semester – Forår 201211B02 Risikovurdering i kemisk industri eller11B03 Risikostyring (valgfrit) 11B13 Brandteknisk dimensionering11B26 Brandmodellering 2 ‐ eller11B27 Komplekse bygninger (valgfrit)
4. Semester – Efterår 201211B17 Brandteknisk projektopgave
Satellitkursus11B28 Modellering af bygninger ved brand 11B29 Installationer
FIRE SAFETY EDUCATION AT DTU
Master in Fire Safety (MiB):http://www.byg.dtu.dk/Uddannelse/Masteruddannelse/Brandsikkerhed.aspx
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
FIRE SAFETY DAY
Yearly event ‐ Next FSD 12 June 2014
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of Denmark
FIRE SAFETY DESIGN OF STEEL STRUCTURES
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of Denmark
I. Motivation and strategies: Fire cases, fire phases and fire design strategies (active and passive measures)
II. Approaches and methodology: Design approaches and design steps for structural fire safety
IV. Problems: Effects of thermal expansion and large displacements on collapse modes
FIRE SAFETY DESIGN OF STEEL STRUCTURES
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Højbro Plads, Christiansborg fire 1884
http://indenforvoldene.dk/hoejbro%20plads.html
Development of fire safety design in Scandinavia
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Firestorms
DARMSTADT, 1944 DRESDEN, 1945
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Firewalls and errors
HAZARD
IN-D
EPTH D
EFENCE
HOLES DUE TOACTIVE ERRORS
HOLES DUE TOHIDDEN ERRORS
Usage & maintenance
Fire detection
Fire suppression
Fire resistance
Collapse resistancePASSIVE
ACTIVE
ALIVE
Structural characteristics
The Swiss cheese model
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
robustness
Y
N collapse
activeprotectio
n
passiveprotection
no failures
doesn’t trigger
Y
N
Y
N
spreads
extinguishes
damages
Y
N
no collapse
triggers
prevention
1 42 3
Fire safety strategies
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Mandarin oriental hotel, Beijing 2009Built: under construction Height: 44 floors, 158 mUse: hotel, not occupied yetStructure: steel‐framed with concrete coreFire: triggered at roof, spread downwardsCause: unauthorized fireworkDuration: 5 hoursInjuries: 1 casualty (fireman), 7 injuriesDamages: many floors, no frame, ca. $100mil
Examples of accidental fires
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Tamweel Towers , Dubai 2012Built: 2009 ‐ faulty sprinklersHeight: 35 storeyUse: office and apartmentsStructure: concrete, alum. & fiberglass cladd.Fire: spread due to flammable claddingCause: cigarette butt thrown in a pile of
waste materials left on a balconyInjuries: none, but 61 cars from debris!
Examples of accidental fire
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
robustness
Y
N collapse
activeprotectio
n
passiveprotection
no failures
doesn’t trigger
Y
N
Y
N
spreads
extinguishes
damages
Y
N
no collapse
triggers
prevention
1 42 3
Fire safety strategies
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
First Interstate Bank, Los Angeles 1988Built: 1973, sprinkler systemHeight: 62 floorsUse: office and publicStructure: protected steel Fire: triggered at 12th, vertical spread i4 floors Cause: electrical? – sprinklers not fully activeDuration: 3 and ½ hoursInjuries: 1 casualty, 49 injuriesDamages: not in main structural members, $50 mil.
Example of fire spread
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Grozny Building, Cechnya 2013Built: 2011 (SPRINKLER?)Height: 140 m ‐ 40 story
303 m ‐ 65Use: hotel and apartmentsFire: spread due to combustible part
of insulationCause: short circuit / human errorDuration: 8 hoursInjuries: none (not occupied)Damages: only façade, interior untouched
Example of fire spread
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
robustness
Y
N collapse
activeprotectio
n
passiveprotection
no failures
doesn’t trigger
Y
N
Y
N
spreads
extinguishes
damages
Y
N
no collapse
triggers
prevention
1 42 3
Fire safety strategies
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
www.davidicke.com/forum/showthread.php?t=85545
STILL STANDING!
Example of fire induced damages
Andraus Building ‐ Sao Paulo, 1972Andraus Building, Sao Paulo 1972Built: 1962Height: 15 m, 32 floors – no sprinklerUse: officesStructure: concrete frame and wallsFire: started at 3rd floor ‐ spread to 27th
in 25 min – due to open stairs and plywood in slab formwork
Cause: electrical system overload (?) Injuries: 16 casualties (jumpers), 330 inj.
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Example of fire induced damages
www.davidicke.com/forum/showthread.php?t=85545
STILL STANDING!
Joelma Building ‐ Sao Paulo, 1974
Fire Disasters ‐ CookeOnFire.comwww.cookeonfire.com/pdfs/Joelma.pdf
Joelma Building, Sao Paulo 1974Built: 1972 ‐ no sprinklerHeight: 25 floorsStructure: R.C. concrete, banking companyFire: triggered ta 12th floor – spread
upwards due to flammable interiors
Duration: 4 h and 30 minCause: short circuit Injuries: 180‐190
casualties (40 jumpers)
www.hispanicallyspeakingnews.com/latin‐american‐history/details/
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
robustness
Y
N collapse
activeprotectio
n
passiveprotection
no failures
doesn’t trigger
Y
N
Y
N
spreads
extinguishes
damages
Y
N
no collapse
triggers
prevention
1 42 3
Fire safety strategies
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Examples of fire induced collapses
Windsor Tower, Madrid 2005Built: 1979, fire prot. under constructionHeight: 106 m, 32 floorsUse: office buildingStructure: concrete core and steel columnsFire: triggered at 21st, vertical spreadCause: short‐circuit/arson? ‐ partial insulationDuration: 24 hoursInjuries: 7 firemen, no casualtiesDamages collapse of upper part, collapse standstill!
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Technical University, Delft 2008Built: ‘70enties, no sprinkler systemHeight: 13 floorsUse: office buildingStructure: concreteFire: triggered at 6th floor, spread
upwards Cause: coffee machine short circuitDuration: 7 hoursInjuries: no, thanks to rapid evacuationDamages: major collapse of northern wing,
only vertical propagation
Examples of fire induced collapses
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Firedevelopment
Evacuationand rescue
Structuralbehavior
Compartmentmentaliz.
PC susceptibilityEscape/access routes
SAFETY OFPEOPLE
STRUCTURAL INTEGRITY
Safety of people and properties
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
passive
Create fire compartments
Prevent damage in the elements
Prevent loss of functionality in the building
Structure
Fire Safety Strategies
active
Detection measures(smoke, heat, flame detectors)
Suppression measures (sprinklers, fire extinguisher, standpipes, firemen)
Smoke and heat evacuation system
prevention protection robustness
Limit ignitionsources
Limit hazardous human behavior
Emergency procedure and evacuation
Prevent the propagation of collapse, once local damages occurred (e.g. redundancy)
People
Fire safety strategies
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
A) when heat source comes in contact to a combustible material
B) when it involves adjacent materials
C) when all materials participate to combustion
D) when the maximum temperature is reached
PROPAGATION GROWTH PHASE
FLASHOVER FULLY DEVELOPED PHASE
Q
Structural fire
IGNITION INCIPIENT PHASE
PEAK EXTINCTION PHASEA
TRANSITIONFROM CONTENT
TO STRUCTURAL FIRE
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Flashoverceiling jet
rollover
flashover
STRUCTUREFIRE
CONTENTFIRE
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
NIST ‐ Flashover Room Fires
Ceiling jet, rollover, flashover: total time 45 seconds
http://www.youtube.com/watch?v=QqMVm72FMRk
Flashover
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
FlashoverDefinition:‐ flashover occurs when the entire room contents ignite simultaneously
Criterion:‐ Babrauskas criterion: 600°C and 20kW/m2
UPPER AND LOWER LAYER
(TWO‐ZONES MODEL)
PRE‐FLASHOVER POST‐FLASHOVER
Design fires
SAME TEMPERATURE IN THE WHOLE COMPARTMENT
(ONE ZONE MODEL)
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Post‐flashover phases
PRE‐FLASHOVER POST‐FLASHOVER
Post‐flashover models
DESIGNmonotonically increasing
PARAMETRICwith cooling phase
DECAY:fire temperature decreases –NOT structure temperature!
analyticalmodels
fire tests(conventional)
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of Denmark
I. Motivation: Fire cases, fire phases and fire design strategies (active and passive measures)
II. Approaches and methodology: Design approaches and design steps for structural fire safety
FIRE SAFETY DESIGN OF STEEL STRUCTURES
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Design approaches
Structural fire safety
b. against failure c. against collapsea. for time resistance
a. RESISTANCE CLASS b. FULLY DEVELOPED FIRE
verifications for all durationof a compartment fire
(parametric fire – hand calculations)
BUILDING RESPONSE
verifications ofconventional collapse
for different fire scenarios
(PB! Often natural fire – FEM)
Structural behaviour afterdesign time is unknown
Integrity of the structure
verifications for alimited time of standard fire
(nominal fire ‐ hand calculations)
WELL‐ESTABLISHED PROCEDURE ADVANCED DESIGN
design
complexity
knowledge
b. FULLY DEVELOPED FIRE c. BUILDING RESPONSE
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
2
Design methodology
modeling of fire action1
heat transmission 2
material properties3
structural behaviour4
1
Fire design processFIRE ACTION
FIRE COURSE
1
ELEMENT TEMPERATURE
2
MATERIAL DEGRADATION
3
VERIFICATIONOR DESIGN
4
Ponticelli&Caciolai, 2008
RESISTAN
CESTIFFN
ESS
3
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
DESIGN APPROACH
METHODOLOGYa. Resist. class b. Fully developed fire c. PBFD
1. Fire curveNominal Parametric Natural
Standard EN DS SW CFD
2. Heating curve Expression for protected/unprotected steel Heat transfer
3. Material behavior Effective yielding Proof stress Realistic
4. Verification
Safetycoeff.
Mat. Charact. Charact. Design Design Realistic
Load Greater reduction Lower reduction Effective
Check level Section Section Section Element Structure
Check type Time of resistance Resist. Tcritical Res./Displ. Conventional
collapse
Structural fire safety: methodology
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Structural fire design: main steps
modeling of fire action1
1
Fire design processFIRE ACTION
FIRE COURSE
1
Ponticelli&Caciolai, 2008
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
medium‐sizeoffices DK NL LUX FR UK
‐‐ R60 R90 R120 R120
R90 R90 R120 R120 no
Time [min]
STANDARD FIRE CURVE
resistance classes givenfor type of usage
Ysprinkler
N
0
200
400
600
800
1000
1200
0 20 40 60 80 100 120
R60 945 ̊CR30 842 ̊CR15 739 ̊C R60 945 ̊CR30 842 ̊CR15 739 ̊C R90 1006 ̊C R120 1049 ̊C
1a. Fire action: standard curve
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
1b. Fire action: parametric curves
SW parametric EN parametricDS parametricPARAMETRIC FIRES
0
200
400
600
800
1000
1200
0 10 20 30 40 50 60 70 80 90
Tempe
rature ‐ Fire load
‐ Fire growth rate
FUEL
‐ Opening factor‐ Thermal inertia
COMPARTMENT
Properties of the
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
1c. Fire action: natural curves
Initial phase: fire affected by combustible type
Final phase: cooling due to combustible exhaustion
Central phase: fire controlled by ventilation
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
2
Structural fire design: main steps
modeling of fire action1
heat transmission 2
1
Fire design processFIRE ACTION
FIRE COURSE
1
ELEMENT TEMPERATURE
2
Ponticelli&Caciolai, 2008
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
2a. Steel heating curve: monotonic
0
200
400
600
800
1000
1200
0 10 20 30 40 50 60 70 80 90 100 110 120
UNINSULATED STEEL
INSULATED STEEL
Critical temperature
UNIFORM TEMPERATURE DISTRIBUTION ASSUMED!
t )T - (T VF
c T T 1-i
s*
gs
s1-i
sp,s
*1-i
si
s
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
2b. Steel heating curve: cooling phase
0
200
400
600
800
1000
1200
0 10 20 30 40 50 60 70 80 90
Critical temperature
UNIFORM TEMPERATURE DISTRIBUTION ASSUMED!
t )T - (T VF
c T T 1-i
s*
gs
s1-i
sp,s
*1-i
si
s
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
2c. Advanced heat transfer
‐ to the element surface(thermal map from CFD code)
‐ into element sections(heat transfer in 2D FEs)
‐ along structural elements(heat transfer analysis)
THERMAL ANALYSIS
TEMPERATURE EVOLUTION
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Heat transfer problem
conduction
conduction
Ts (x,t)Toradiation
T1 (t)
ABSORBED BY WALLS
EXCHANGEDBY AIR FLOW
RADIATED THROUGH OPENINGS
Tg (t)convection
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Heat transfer problem for steel
conduction
radiation
T1 (t)
ABSORBED BY WALLS
EXCHANGEDBY AIR FLOW
RADIATED THROUGH OPENINGS
Tg (t)convection
To
Ts (x, t)
Ts (t) = T1
s (t) = 30 W/(m K)
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Heating curve of uninsulated steel
Tg (t)
To
Ts (t)
Ts (t)
convection
radiation
Tg ‐ Ts
ΔT V c ρ Δt )T ‐ (T F α ssp,sssgs
Δt )T ‐ (T VF
c ρα
ΔT sgs
s
p,sss
NUMERICAL SOLUTION
Ts = Ts (Ts)
= (Ts)
cp,s = cp,s (Ts)
ΔU ΔQ
increment of internal energy [J]heat ceased in a time interval [J]
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Insulated steelINTUMESCENT PAINT
after fire
Ponticelli&Caciolai, 2008
before fire
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Thermal resistance of the insulation
VARIES WITH THE TEMPERATURE!!
To
Ts (t)
Ts (t)
Tg (t) Tin (t)
conduction
THICKNESS OF INTUMESCENT PAINT VARIES TOO…
din(t)
high expansion intumescentbefore and after furnace heating
MSc PROJECTAT DTU!
CONDUCTIVITY VARIES WITH TEMPERATURE…
Insulated steel
TR = din / in [m2 K / W]
insulation conductivity [W/(m K)]
insulation thickness [m]
in in (Tin (x, t)) in in (Tin (t))din = thin
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
2
Structural fire design: main steps
modeling of fire action1 material properties3
1
Fire design processFIRE ACTION
FIRE COURSE
1
ELEMENT TEMPERATURE
2
MATERIAL DEGRADATION
3
Ponticelli&Caciolai, 2008
RESISTAN
CESTIFFN
ESS
3
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Steel mechanical properties degradation
T
<=100°C200°C
400°C
600°C
800°C
500°C
EC 1‐2
2%
20%0.2% 15%
sw B52
fyk
STIFFNESS, ELASTIC LIMIT, RESISTANCE
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
fyT
500°C
2%
20%15%
fpT
p
20°Cfy
E
ET
Degradation of stiffness and resistance
2% stress considered for yielding
3a. Material behavior: steel degradation
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
500°C
20%0.2%
15%
f0.2T
fpT
p
20°Cfy
E
ET
Degradation of stiffness and resistance
0.2% proof stress considered for yielding
3b. Material behavior: steel degradation
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
3. Material behavior: steel degradation
0
0,2
0,4
0,6
0,8
1
1,2
0 100 200 300 400 500 600
Resistance
Stiffness
0
0,2
0,4
0,6
0,8
1
1,2
0 200 400 600 800 1000 1200
Resistance
Stiffness
1) EUROCODES 2) SWEDISH METHODNATIONAL DANISH ANNEX
2.0% effective yield stress 0.2% proof stressRESISTANCE
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Degradation of stiffness and resistance
Elastic‐perfectly plastic with hardening
500°C
20%u
fuT
fpT
p
20°Cfy
E
ET
3c. Material behavior: steel degradation
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
2
Structural fire design: main steps
modeling of fire action1
heat transmission 2
material properties3
structural behaviour4
1
Fire design processFIRE ACTION
FIRE COURSE
1
ELEMENT TEMPERATURE
2
MATERIAL DEGRADATION
3
VERIFICATIONOR DESIGN
4
Ponticelli&Caciolai, 2008
RESISTAN
CESTIFFN
ESS
3
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
5% fractile
of 0.2% proof stress
charact. value
fyd = fyk / γm
γm = 1.0
medium value
fyd = fym / γm
γm = 1.0
most probable yielding resistance
+ hardening!
b. FULLY DEVELOPED c. PBFD
charact. value
fyd = fyk / γm
γm = 1.0
a. RESISTANCE CLASSES
5% fractile
of 2.0% effective yield stress
4. Verification: material safety coefficients
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
4. Verification: load safety coefficients
Ultimate Limits state (ULS)
Accidental Limit State (ALS)
LOAD COEFF. Gk Qk1 Qki Gk Qk1 Qki
EUROCODE 1.35 1.50 1.5∙0.7 1.00 0.60 0.20
DANISHSTANDARD
1.00 1.30 0.50 1.00 1.00 0.50
Ultimate Limits state (ULS)
Accidental Limit State (ALS) ALS/ULS
EUROCODE 8.49 kN/m2 4.55 kN/m2 0.54
DANISHSTANDARD
7.15 kN/m2 6.25 kN/m2 0.87
SAFETYCOEFFICIENTS
EXAMPLE OFFLOOR LOAD
DS: conservativeALS loads
EN: conservativeULS loads
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
4. Verification: collapse criterion
severity
complexity
STRUCTUREPBFD (displacement limits)
max < L/20
max < L2 / 800 H
SECTION ULSALS (Eurocodes)
Mu
ELEMENTALS(Swedish method)
Pu
FIBERSLS(+ deform. check)
y
LEVEL OF VERIFICATION
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures
Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of Denmark
I. Motivation and strategies: Fire cases, fire phases and fire design strategies (active and passive measures)
II. Approaches and methodology: Design approaches and design steps for structural fire safety
IV. Problems: Effects of thermal expansion and large displacements on collapse modes
FIRE SAFETY DESIGN OF STEEL STRUCTURES
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
Structural analysis issues
THERMAL EXPANSION
INDIRECT STRESSES
THERMAL EFFECTSA
LARGE DISPLACEMETSB
COLLAPSE CRITERIONC
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
A. Thermal expansion
relative thermal elongation (L/L0 ) = ∙ T [ad.]
therm = (T) ∙ T [ad.]
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
A. Thermal expansion
relative thermal elongation
Ltherm/L = (T) ∙ T [ad.]
thermal expansion coefficient [K‐1]
Total deformation: tot = therm(T) + mech(,T)
not hindered hindered
elongation+
induced deformation
partially hindered
elongation and compression+
induced deformation and stresses
eigenstresses
eigen(T, ET) Ltherm(T)
eigen = kET E20 Lfree /L
compression+
induced stresses
RESTRAIN GRADE
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
A. Thermal expansion
Total deformation: tot = therm(T) + mech(,T)
hindered
eigenstresses
eigen(T, ET) Ltherm(T)
eigen = kET E20 Lfree /L
compression+
induced stresses
relative thermal elongation
Ltherm/L = (T) ∙ T [ad.]
thermal expansion coefficient [K‐1]
not hindered
elongation+
induced deformation
partially hindered
elongation and compression+
induced deformation and stresses
Lreal = ∙ lfree
eigen = kET E20 (1 ‐ ∙ Lfree /L
RESTRAIN GRADE
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
A. Indirect stresses
LC hind
N
LB,real
N + N
LC
a b
LB
ΔLΔL
ΔLhinderedrealized
realized
restrain
coefficient free
realized
ΔLΔL
γ
KΔN
ΔL TflexB,
realized T
C,ax
hindered
KΔN
ΔL
displacement of the beam displacement of the column
TC,ax
TflexB,
KK1
1γ
hideredtotally 0KK
freetotally 1KK
Tax,C
Tflex,B
Tflex,B
Tax,C
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
A. Indirect stresses
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1,0
0 0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08 0,09 0,1
K
hinged at both ends clumped at both ends
K4811
γ
K 19211
γ
CCC
3BBB
/LAELIE
K
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
A. Indirect stressesdesign of columnLoad bearing capacity of restrained columns is much lower!!
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
A. Indirect stresses
indirect stresses
DISREGARDED
in case standard fire is used
severe fire
verification on single members without effect of adjacent element
CONSIDERED
for buckling verification
verification on single columns,but effect of adjacent element is considered
EC 1‐2sw B52
L
ΔL‐1EΔσ
freeT
eigen
TC,ax
TflexB,
KK1
1γ
0 eigen∆σ ISO834
t
T
L E1
E1
AN
T ΔL 20Tfree
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
THERMAL EXPANSION
INDIRECT STRESSES
BOWING EFFECT
CATENARY/MEMBR. ACTION
possible overloading of elements
higher displacements induced
THERMAL EFFECTSA
LARGE DISPLACEMETSB
COLLAPSE CONDITIONC
Structural analysis issues
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
WHEN DISPLACEMENT ARE LARGE
THESE BEAMS BEHAVE DIFFERENTLY
UNDER VERTICAL LOADS
B. Large displacements
Q
L
horizontally restrained
L
simply supported
1. A vertically loaded simply supported beam is exposed to fire. The sliding support:a. will stay stillb. will move to the right (toward the outside)c. will move to the left (toward the other support)
2. What would happen if the beam were horizontally restrained instead?
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
1. A vertically loaded simply supported beam is exposed to fire. The sliding support:a. will stay stillb. will move to the right (toward the outside)c. will move to the left (toward the other support)
2. What would happen if the beam were horizontally restrained instead?
Q
L
horizontally restrained
L
simply supported
A
N N
first expansionthen contraction
first compressionthen tension
B. Large displacements
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
simply supported beam horizontally restrained beam
q q
T T
tension catenary actionLD prevails bowing effect2
compression II ord. momentthermal effect prevails expansion1
B. Large displacements
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
THERMAL EXPANSION
INDIRECT STRESSES
BOWING EFFECT
CATENARY/MEMBR. ACTION
possible overloading of elements
higher displacements induced
THERMAL EFFECTSA
LARGE DISPLACEMETSB
COLLAPSE MODEC
LOW RESTRAIN
HIGH RESTRAIN
possible loss of supports
generally beneficial for members
Structural analysis issues
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Luisa Giuliani ‐ Fire safety design of steel structures
B. Collapse mode: sway collapse of industrial hall
Denmark 2013 Romania 2010
Alexandru Dondera, MSc thesis, 2013
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Luisa Giuliani ‐ Fire safety design of steel structures
B. Collapse mode: early beam buckling of tall buildings
‐200
‐100
0
100
200
300
400
500
600
700
0 100 200 300 400 500 600 700 800 900 1.000
Axial Force (k
N)
Temperature (°C)
THERMAL BUCKLING
PLASTIC HINGE
TENSILE COLLAPSE
IPE 270HE 1000 M
= 0.9
HIGH RE
STRA
INT
LOW RESTR
AINT
Riccardo Aiuti, MSc thesis, 2013
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
WTC, Usmani&al.2003
B. Collapse mode: vertical propagation
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Luisa Giuliani ‐ Fire safety design of steel structures
Motivation
Prob
lems
Approa
ch and
metho
dology
THERMAL EXPANSION
INDIRECT STRESSES
BOWING EFFECT
CATENARY/MEMBR. ACTION
possible overloading of elements
higher displacements induced
THERMAL EFFECTSA
LARGE DISPLACEMETSB
COLLAPSE MODEC
LOW RESTRAIN
HIGH RESTRAIN
possible loss of supports
generally beneficial for members
Sway collapse
Early buckling, possible PC
Structural analysis issues
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Luisa GiulianiAssistant Professor, Ph.D., P.E.
DTU ‐ BYGCivil Engineering Department
Technical University of DenmarkFire sa
fety design of steel structures I. Motivation and strategies:
Explain why structural fire safety is important, and which fire phases are involved,what is flashover and why it allows for one‐zone model assumption in post FO models
II. Approaches and methodology:Name three different design approach for structural fire safety and explain the maindifference in each of the 4 design steps for structural verification and design.
IV. Problems:Explain how mutual stiffness of beams and columns and large displacementsdetermines sway collapse and buckling collapse of steel structures.
LEARNING OBJECTIVES