21
BRE Centre for Fire Safety Engineering THE UNIVERSITY of EDINBURGH United Kingdom Xu Dai Authors: Xu Dai, StephenWelch, Asif Usmani A critical review of “travelling fire” scenarios for performance-based structural engineering

A critical review of “travelling fire” g - FSMF.UK · A critical review of “travelling fire” ... Gas burners, or wood cribs Wood ... ‘Performance-Based Fire Engineering

  • Upload
    trandan

  • View
    219

  • Download
    2

Embed Size (px)

Citation preview

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

THE UNIVERSITY of EDINBURGH

United Kingdom

Xu DaiAuthors: Xu Dai, Stephen Welch, Asif Usmani

A critical review of “travelling fire”

scenarios for performance-based

structural engineering

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Motivation

Fire uncertainties to large spaces architecture

for structural design?

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

IntroductionWindsor Tower in Madrid in 2005 World Trade Center Tower 1

in New York City in 2001

(source: https://www.metabunk.org/)

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

WTC 7

2:57 p.m. 3:05 p.m.

3:13 p.m. 3:44 p.m.

Fire visible inside Not visibleWindow glass intact Window open

(source: NIST NCSTAR 1-9, Structural Fire Response and Probable Collapse

Sequence of World Trade Centre Building 7, 2008)

Facade map summarizing observations of fire spread

and window breakage on the north face of WTC 7

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Introduction

What is a travelling fire?

It is a way of approximating fire impact on structures

in large open-plan spaces for structural design.

Large compartment fires may burn locally and tend to

move across floor plates over a period of time.

Alternative names:

moving fires, spreading fires, real fires, natural fires, non-uniform fires…

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Travelling fire experiments

Experiments

Kirby & Cooke, 1993

LBTF – Demonstration Furniture, 1995–1996

Thomas et al., 2005

NFSC - BRE Cardington, 1999–2000

St. Lawrence Burns project, 1958

Veselí Travelling Fire Test, 2011

BRE Travelling Fire Test, 2013

Tisová Travelling Fire Test, 2015

• Labelled as ‘travelling fire tests’

• Fire tests that have a ‘spreading’ nature

before 2010

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Veselí travelling fire test

Experimental building during travelling fire test

(source: photo provided by Horová K., CVUT in Prague)

Fuel load scheme, in hatched, on the upper floor of the

experimental building

(source: F. Wald et al., CVUT in Prague)

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Veselí travelling fire test

5 minutes10 minutes15 minutes20 minutes25 minutes30 minutes35 minutes40 minutes

Development of the fire during the test(source:photos provided by Horová K., CVUT in Prague)

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Travelling fire experiments

Experiments

Kirby & Cooke, 1993

LBTF – Demonstration

Furniture, 1995–1996

Thomas et al., 2005

NFSC - BRE Cardington,

1999–2000

St. Lawrence Burns

project, 1958

Veselí Travelling Fire

Test, 2011

BRE Travelling Fire

Test, 2013

Tisová Travelling Fire

Test, 2015

Categories

Dimensions

22.8 m × 5.6 m × 2.75 m

135 𝐦𝟐

230 𝐦𝟐× 4.4 m

5 m × 18 m × 2 m

10.4 m × 13.4 m × 4 m

11.2 m × 12.8 m, and

13 m × 9 m

8.m × 2.m × 0.6 m

12 m × 12 m × 3 m

Fuel load

Wood cribs

Furniture

Commercial grade

methylated spirits

Wood waste

Wood waste

Gas burners,

or wood cribs

Wood cribs +

Hydrocarbon accelerant

Wood cribs, or 80% wood

cribs + 20% plastic

Thermal

response

Gas and steel

temperatures

Gas and steel

temperatures

Gas and steel

temperatures

Gas temperatures

Gas, steel, and

concrete temperatures

Gas temperatures

Gas and concrete

temperatures

Gas and steel

temperatures

Structural

response

None

Strain and

deflections

None

None

Strain and

deflections

N/A

Deflections

None

Mass loss

measurement

Yes

No

Yes

No

No

Yes

No

Yes

Summaries of the experiments reviewed for travelling fires

Fire

Engineering

Structural

Engineering

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Fire ‘hierarchy’ for structural design

Fire Structural Design

Inc

reas

ing

un

ce

rtai

nti

es

for

app

lic

atio

n Standard fire curve

Parametric fire curves

Zone models

Localised fire models

CFD models

Travelling fires

Prescriptive design

Performance-based

design

Thermal loading

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Travelling fire analytical models

How to bring travelling fires into

structural design ?

• Clifton’s travelling fire model

• Rein’s travelling fire model

• Extended Travelling Fire Method (ETFM) framework

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Travelling fire analytical models

Clifton’s travelling fire model

60m

36m

0 min 20 min

40 min 60 min

Fire Preheating Cooling

Conceptual illustration of Clifton’s model

(source: adapted from Y. Wang et al., 2012)

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Travelling fire analytical models

Rein’s travelling fire model

Illustration of a travelling fire and distribution

of gas temperatures

(source: E. Rackauskaite et al., 2015)

Near field:

Far field :

Alpert’s ceiling jetFlapping angle and reduced near field temperature

(source: E. Rackauskaite et al., 2015)

800℃ −1200℃, flapping angle1200℃

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Travelling fire analytical models

Ceiling‘Combination’ of localized fire model & zone model0

heat flux

local fire

Smoke layer depth d = d (t)

Steel Beam

Pre-heating Post-heatingDirect exposure

Extended Travelling Fire Method (ETFM) framework

e.g. - Hasemi’s localised fire external heat flux ሶℎ (W/m2) : e.g. - FIRM zone model:

Based on M. Janssens’ book, 2000

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Travelling fire analytical models

Far field temperature

(i.e. smoke)

Fire path

Smoke accumulation

Spread rate

Non-uniform fuel

Fire size

HRR consideration

Mass conservation

Energy conservation

Compartment boundary

Ventilation/fuel controlled

Firecell to neighboured ones

No

From observation

No

Decided by fuel load density

No

No

No

Yes

Ventilation controlled

Not defined

No

From observation

No

Decided by fuel & fire spread

Yes

Yes

No

No

Fuel controlled

Alpert’s ceiling jet model

Categories Models

Clifton’s Travelling Fire Model

Summaries of the travelling fire analytical models

Rein’s Travelling Fire Model ETFM Framework

Near field

temperature

Time-temperature

curve for firecells800℃ −1200℃, flapping angle Localised fire model (e.g. Hasemi)

Predefined trajectory

Yes

From observation

Yes

Decided by fuel & fire spread

Yes

Yes

Yes

Yes

Fuel & ventilation controlled

Simple zone model (e.g. FIRM)

Flashover Yes No Yes

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Fire ‘hierarchy’ for structural design

Fire Structural Design

Inc

reas

ing

un

ce

rtai

nti

es

for

app

lic

atio

n

Standard fire curve

CFD models

Prescriptive design

Performance-based

design

Parametric fire curves

Localised fire models

Zone models

Clifton’s travelling fire

model

Rein’s travelling fire

model

ETFM framework

Structural AnalysisThermal loading

Heat Transfer

Tabulated results

‘Lumped mass’

calculations

1-D uncoupled

heat transfer

Coupled heat transfer

- mechanical analyses

2-D or 3-D uncoupled

heat transfer

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Case study using ETFM framework

An idealised steel composite building with a core

Visualization output of OpenSees-SIFBuilder during heat transfer analysis

x direction: 6m – 9m – 9m – 6m z direction: 6m – 9m – 6my direction: 5m – 4m

y

xz

Building dimensions:Fire spread rate: 10 mm/s

Fuel load density: 570 MJ/m2HRR per area: 500 kW/m2

Base line fire scenario: Net floor area: 468 m2 Clear floor height: 3.85 mLarge compartment dimensions:

Total vent width: 28 m Soffit height: 3 m Sill height: 1 mFire starts on the first floor

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

100 MJ/m2

230 MJ/m2

300 MJ/m2

420 MJ/m2

600 MJ/m2

780 MJ/m2

Case study using ETFM framework

Two key input variables for ETFM: fire spread rates, and fuel load densitiesTravelling fires with changing fuel load densities

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Fire ‘hierarchy’ for structural design

Fire

Inc

reas

ing

un

ce

rtai

nti

es

for

app

lic

atio

n Standard fire curve

CFD models

Prescriptive design

Performance-based

design

Parametric fire curves

Localised fire models

Zone models

Clifton’s travelling fire

model

Rein’s travelling fire

model

ETFM framework

Structural AnalysisThermal loading

Heat Transfer

Tabulated results

‘Lumped mass’

calculations

1-D uncoupled

heat transfer

Coupled heat transfer

- mechanical analyses

2-D or 3-D uncoupled

heat transfer

Tabulated results

Limiting temperature

or strength

Simplified methods

Dynamic analyses

Static and quasi-static

analyses

(source: adapted from Y. Wang et al., ‘Performance-Based Fire Engineering of Structures’, 2012)

Progress so far…

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Consistent level of complexities/crudeness/efficiency

for

fire – heat transfer – structural analysis

Fire uncertainties to large spaces architecture

for structural design?

BR

E C

en

tre for

Fir

e S

afe

ty E

ngin

eeri

ng

Future work

TRAFIR ProjectCharacterization of TRAvelling FIRes in large compartments

• testing (isolated elements and simplified fire

progression, as well as a full-scale large compartment)

Eight work packages (1/07/2017 → 31/12/2020):

• modelling (both simplified analytical/phenomenological

models and CFD).

Project partners:

Funding from the Research Fund for Coal and Steel (RFCS) - European Commission