PART 1 THERMAL & MECHANICAL ACTIONS - Constructalia

DIF SEK PART 1 THERMAL & MECHANICAL ACTIONS DIF SEK

Part 1: Thermal & Mechanical Actions

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Resistance to Fire - Chain of Events Loads

Θ Steel columns

time

1: Ignition

2: Thermal action

3: Mechanical actions

R

time

4: Thermal response

DIF SEK

5: Mechanical response Part 1: Thermal & Mechanical Actions

6: Possible collapse 1

Structural Fire Safety Engineering vs. Classification Prescriptive

DIF SEK

Performance based

standard fire

natural fire

classification

fire safety eng.

fire safety eng.

fire safety eng.


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Actions on Structures Exposed to Fire EN 1991-1-2 - Prescriptive Rules

Design Procedures

Prescriptive Rules (Thermal Actions given

by Nominal Fire)

DIF SEK

Performance-Based Code (Physically based Thermal Actions)


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Nominal Temperature-Time Curve *) Nominal temperature-time curve Standard temperature-, External fire - & Hydrocarbon fire curve

No data needed

*) Simplified Fire Models Localised Fire Fully Engulfed Compartment - HESKESTADT - HASEMI

- Parametric Fire θ (t) uniform in the compartment

θ (x, y, z, t)

Rate of heat release Fire surface Boundary properties Opening area Ceiling height

*) Advanced Fire Models - One-Zone Model - Two-Zone Model - Combined Two-Zones and One-Zone fire

+ Exact geometry

- CFD

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Prescriptive Fire Regulations Defining ISO Curve Requirements ISO-834 Curve (EN1364 -1) T = 20 + 345 log (8 t + 1)

θ [°C]

1200

1110 1006

1000

945

1049 The ISO curve * Has to be considered in the WHOLE compartment, even if the compartment

842 800

is huge

600

ISO ISO

400

ISO * Never goes DOWN

ISO ISO

Time [min]

ISO

* does not consider the PRE-FLASHOVER PHASE

200 0

ISO

ISO

* Does not depend on FIRE LOAD and VENTILATION CONDITIONS 0

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30

60

90

120

180


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Stages of a Natural Fire and the Standard Fire Curve Temperature Pre- Flashover

Post- Flashover 1000-1200°C

Flashover

Natural fire curve

ISO834 standard fire curve

Time Ignition - Smouldering

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Heating

Cooling ….


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Fire Protection Standard fire approach requires Fire protection in most cases F30 may be achievable without protection

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Actions on Structures Exposed to Fire EN 1991-1-2 - Performance Based Code

Design Procedures

Prescriptive Rules

Performance-Based Code

(Thermal Actions given

(Physically based Thermal Actions)

by Nominal Fire)

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History Natural Fire Safety Concept Validation with real fire tests Statistics oninto realEurocodes Fires Implementation

Development of NFSC Concept Fire Growth

Probability of Occupancy

st

[MJ/m²]

Dwelling Hospital (room) Hotel (room) Library Office School Shopping Centre Theatre (movie/cinema) Transport (public space)

fail

p O&SFB [-]

-6

Industrial Building 10 0,05 to 0,1 • Some National10 Fire Regulations -6 10 10 Office 0,02 to 0,04 include now alternative requirements -6 Dwellings 30 10 0,0125 to 0,025 based on Natural Fire Based on Statistics : - in the Canton of Bern during 10 years (39104 fires); - in Finland during the year 1995 (2109 fires) and - in France during the year 1995 (82179 fires) and on values given in the standards : - DIN 18230 "Structural fire protection in Industrial Buildings"; - BSI document DD240 Part 1 "Fire safety engineering in Buildings".

Fire Load q f,k

[kW/m²]

Fire Occurence Failure of Occupants or Starting Fire & Standard Firemen in stopping the fire p fi [1/(m².year)]

RHR f

Occupancy Rate 80% fractile Calibration of Design Software 250 250 250 500 250 250 250 500 250

948 280 377 1824 511 347 730 365 122

IS O cu rv e

θ [°C]

1200

Medium Medium Medium Fast Medium Medium Fast Fast Slow

1000 800 600 400 200 0

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0

30

60

90


180 120 Time [min]

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NFSC Valorisation Project

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Natural Fire Model *) Nominal temperature-time curve Standard temperature-, External fire - & Hydrocarbon fire curve

No data needed



θ (x, y, z, t)



+ Exact geometry

- CFD

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List of needed Physical Parameters for Natural Fire Model ! Boundary properties ! Ceiling height

Geometry

! Opening Area ! Fire surface ! Rate of heat release

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Fire


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Characteristics of the Fire Compartment Fire resistant enclosures defining the fire compartment according to the national regulations

Material properties of enclosures: c, ρ, λ

Definition of Openings

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Characteristic of the Fire for Different Buildings

Occupancy

Fire Growth Rate

RHR f

[kW/m²]

Fire Load q 80% fractile f,k [MJ/m²]

Dwelling (room) Hospital Hotel (room) Library Office School Shopping Centre Theatre (movie/cinema) Transport (public space)

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Medium Medium Medium Fast Medium Medium Fast Fast Slow

250 250 250 500 250 250 250 500 250


948 280 377 1824 511 347 730 365 122

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Fire Load Density Danger of Fire Activation

Compartment floor area Af [m²]

δq1

Examples of Occupancies

Danger of Fire Activation

δq2

25

1,10

0,78

Art gallery, museum, swimming pool

250

1,50

1,00

Residence, hotel, office

2500

1,90

1,22

5000

2,00

1,44

10000

2,13

1,66

Manufactory for machinery & engines Chemical laboratory, Painting workshop Manufactory of fireworks or paints

q f , d =δ δ q1 . δ q 2 . ∏ δ ni . m . q f , k ni

Automatic Fire Suppression

Automatic Fire Detection

Automatic Water Extinguishing System

Independent Water Supplies

δ

δ

n1

0,61

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0

1

Function of Active Fire Safety Measures

2

n2

1,0 0,87 0,7

Automatic fire

Automatic Alarm Detection Transmission & Alarm to by by Heat Smoke Fire Brigade δ δ n3 δ n4 n5 0,87 or 0,73

0,87

Manual Fire Suppression

Work Fire Brigade

Off Site Fire Brigade

δ

δ

n6

0,61

or

n7

0,78


Safe Access Routes

δ

n8

0,9 or 1 1,5

Fire Fighting Devices

δ

n9

1,0

Smoke Exhaust System δ

n10

1,0 1,5

1,5

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Rate of Heat Release Curve Stationary State and Decay Phase 10 9

75'' 150''

1

70% (qf,d • Afi) 0 0 0

0

DIF SEK

A f x RHR

0

f

Fast (FGR)

COMPARTMENT FIRE

RHR [MW] RHR [MW]

RHR [MW]

10 Ultra8 9 Fast 7 (FGR) 8 6 7 5 6 4 5 3 4 2 3 2 1

Growing Steady state phase

Medium (FGR)

FireA Growth Rate = FGR x RHR

f

f

Ventilation Controlled Fire Slow (FGR) Decay phase

t [min] Decay Phase

300''

5

600''

10 5

15 10

tdecay


20 15

25t [min]30 20

Time [min]

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Natural Simplified Fire Model *) Nominal temperature-time curve Standard temperature-, External fire - & Hydrocarbon fire curve

No data needed



θ (x, y, z, t)



+ Exact geometry

- CFD

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Simplified Fire Models Fire behaviour LOCALISED FIRE θ (x, y, z, t)

DIF SEK

FULLY ENGULFED COMPARTMENT θ (t) uniform in the compartment


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Simplified Fire Models Localised Fire LOCALISED FIRE

FIRE TEST

θ (x, y, z, t)

TYPICAL APPLICATION

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Localised Fire: HESKESTAD Method Annex C of EN 1991-1-2: • Flame is not impacting the ceiling of a compartment (Lf < H) • Fires in open air

Θ(z) = 20 + 0,25 (0,8 Qc)2/3 (z-z0)-5/3 ≤ 900°C Flame axis

The flame length Lf of a localised fire is given by :

Lf = -1,02 D + 0,0148 Q2/5

H Lf z

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D


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Localised Fire: HASEMI Method Annex C of EN 1991-1-2: • Flame is impacting the ceiling (Lf > H)

concrete slab beam

θg θ

= Air Temperature at Beam Level

Y = Height of the free zone

Calculated by CaPaFi

x

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Simplified Fire Models Fully Engulfed Compartment Fire FULLY ENGULFED COMPARTMENT

FIRE TEST

θ (t) uniform in the compartment

TYPICAL APPLICATION

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Large Compartment Test

Fire load: 40kg of wood / m2

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Fire behaviour Fuel controlled

Ventilation controlled

Most severe conditions 900

RHRf = 250 KW/m² At / Af = 4.5 Unprotected Steel FIRE LOAD:

800 700 600

qf = 50 qf = 100 qf = 200 qf = 300 qf = 400 qf = 500 qf = 600 qf = 700 qf = 800 qf = 900 qf = 1000

Temperature

500 400 300 200 100

0

0.02

0.04

Small opening

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0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Opening-Factor


0.22

0.24

0.26

0.28

Big opening

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Fully Engulfed Compartment Parametric Fire Temperature [°C]

Annex A of EN 1991-1-2 Iso-Curve

1100 1000

O = 0.04 m ½

900

O = 0.06 m ½

800

O = 0.10 m ½ O = 0.14 m ½

700

O = 0.20 m ½

600

For a given b, qfd, At & Af

500 400 300 200 100 0

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0

time [min] 10

20

30

40

50

60

70

80


90

100

110 120

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Natural Advanced Fire Model *) Nominal temperature-time curve Standard temperature-, External fire - & Hydrocarbon fire curve

No data needed



θ (x, y, z, t)



+ Exact geometry

- CFD

DIF SEK


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Advanced fire Models LOCALISED FIRE

The Fire stays localised

The Fire switch to a fully engulfed fire

LOCALISED FIRE

FULLY ENGULFED COMPARTMENT

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Real Fire Test Simulating an Office Building Fully engulfed fire

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Two Zone Calculation Software “OZone V2.2”

Download at www.arcelor.com/sections DIF SEK Part 1: Thermal & Mechanical Actions

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OZone - Results θ Hot θ Cold

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Calibration of Software OZone: Gas Temp 1400 MAXIMUM AIR T EMPERATURE OZone 1200

OZone [°C]

1000

800

600

400

200 MAXIMUM AIR T EMPERATURE IN THE COMPARTMENT 0 0

200

400

600

800

1000

1200

1400

TEST [°C]

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Calibration of Software OZone: Steel Temp 1400 UNPROTECTED STEEL TEMPERATURE 1200

OZone [°C]

1000

800

600

400

200

0 0

200

400

600

800

1000

1200

1400

TEST [°C]

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OZone: Case Study Influence of the Actives Fire Safety Measures 1000

Office : A f = 291,2 m² O.F. = 0,04 m½ ; Fire Load q f,k = 511 MJ/m²

900

No Fire Active Measures

800

Gas temperature [°C]

Off Site Fire Brigade

700

Automatic Fire Detection & Alarm by Smoke Automatic Alarm Transmission to Fire Brigade Automatic Water Extinguishing System

600 500 400

Design Fire Load q f,d [ MJ/m² ]

625 356 310 189

300 200

q f ,d = m δ q1 δ q2 ∏ δ ni q f ,k

100 0

i

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140 150

Time [min]

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Computer Fluid Dynamics (CFD) Not yet widely used! • Not yet user-friendly • Long calculation times

Used in case of: • Complicated geometry (atrium) • Localised fires • Calculation of smoke exhaust

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Resistance to Fire - Chain of Events Loads

Θ Steel columns

time

1: Ignition

2: Thermal action


R

time

4: Thermal response

DIF SEK



Basis of Design and Actions on Structures S

W

Actions for temperature analysis G

A C T I O N S

Q

Thermal Action

FIRE Actions for structural analysis Mechanical Action Dead Load Imposed Load Snow Wind

G Q S W

Fire

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Combination Rules for Mechanical Actions EN 1990: Basis of Structural Design Room temperature E d = γG G + γ

Q,1

Q

1

+ ∑ψ

0,i

γ Q,i Q

i

i >1

f.i. : Offices area with the imposed load Q, the leading variable action E

= 1,35 G + 1,5 Q + 0,6 • 1,5 W + 0,5 • 1,5 S

d

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Combination Rules for Mechanical Actions EN 1990: Basis of Structural Design Fire conditions ≡ Accidental situation = G+ψ

E fi,d

Q +∑ ψ 1or2,1

1

i >1

Qi 2,i

f.i. : Offices area with the imposed load Q, the leading variable action E

= G + 0,5 Q fi,d

Offices area with the wind W, the leading variable action E

= G + 0,2 W + 0,3 Q fi,d

" Maximum Load ratio in fire: 1,0 G / 1,35 G = 0,74

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Values of ψ factors for buildings ψ1

ψ2

0,7 0,7 0,7 0,7 1,0

0,5 0,5 0,7 0,7 0,9

0,3 0,3 0,6 0,6 0,8

0,7

0,7

0,6

0,7 0

0,5 0

0,3 0

0,70 0,70

0,50 0,50

0,20 0,20

0,50

0,20

0

Wind loads on buildings (see EN1991-1.4)

0,6

0,2

0

Temperature (non-fire) in buildings (see EN1991-1.5)

0,6

0,5

0

ψ0

Action Imposed loads in buildings, category (see EN 1991-1.1) Category A : domestic, residential areas Category B : office areas Category C : congregation areas Category D : shopping areas Category E : storage areas Category F : traffic area vehicle weight ≤ 30kN Category G : traffic area, 30 kN < vehicle weight ≤ 160kN Category H : roofs Snow loads on buildings (see EN1991-1.3) Finland, Iceland, Norway, Sweden Remainder of CEN Member States, for sites located at altitude H > 1000 m a.s.l. Remainder of CEN Member States, for sites located at altitude H ≤ 1000 m a.s.l.

DIF SEK

( Reference : EN1990 - February 2002) Part 1: Thermal & Mechanical Actions

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Load Factor γ G Gk + γ Q ,l Qk ,l Load Factor E / Rfi,d,t [-] fi,d

η fi =

Gk + ψ fi Qk ,l Maximal Load level after R30

1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0

50

100

150

200

250

300

350

400

Massivity Am/V [1/m]

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Resistance to fire - Chain of events PREVIEW Loads

Θ Steel columns

time

1: Ignition

2: Thermal action


R

time

4: Thermal response

DIF SEK



Thermal action on structure PREVIEW Composite Slab

DIF SEK

Column


42

Resistance to fire - Chain of events PREVIEW Loads

Θ Steel columns

time

1: Ignition

2: Thermal action


R

time

4: Thermal response

DIF SEK



How structures react to fire PREVIEW ! Temperature rise # thermal expansion + loss of both

stiffness and resistance # additional deformation ⇒ eventual collapse

DIF SEK

t = 0 Θ = 20°C

16 min Θ = 620°C

22 min Θ = 720°C

31 min Θ = 850°C


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