performance-based fire safety engineering: … · performance-based fire safety engineering:...

Performance-Based Fire Safety Engineering:

Challenges and Opportunities

Dr. Thomas Gernay

Gustave Magnel International Award – New activities

SECO – Brussels, Belgium, 1st June 2017

F.R.S.-FNRS, University of Liege, Belgium

Fire safety: a major issue

2

The Great Fire of London in 1666 (unknown artist, c. 1700)

T. Gernay, 2017


3

L’Innovation Fire, Brussels, 1967 World Trade Center attacks, NYC, 2001

T. Gernay, 2017


First and foremost: life safety

But also: property protection, infrastructure protection

Total cost of fire: ≈ 1% of GDP in developed countries1

- Cost of direct fire losses (casualties, property losses, etc.)

- Cost of indirect fire losses (rehousing, business interruption, etc.)

- Cost of fire fighting organizations

- Cost of fire protection to buildings

- Cost of fire insurance administration

4

1Geneva Association World Fire Statistics Centre (WFSC)

T. Gernay, 2017

Fire Safety Engineering: a multidisciplinary field

Structural fire engineering is a key component

Design the structures for adequate response under fire

→ compartmentation and structural stability

5

To achieve the goal in Fire Safety Engineering, it requires implementation

of multiple objectives based on various disciplines

↘ proba of ignition ↘ proba of fire spread allow safe evacuation

T. Gernay, 2017

Prescriptive vs Performance-Based approach

6

Prescribes methods to build vs Prescribes a result (performance)

→ Simplicity vs → Flexibility

PRESCRIPTIVEfollowing codes and standards

PERFORMANCE-BASEDbased on the physics of the problem

DESIGN APPROACHFor a structure against fire hazard

PBD: opportunity for more efficient, economic and elegant design solutions,

but requires a more advanced understanding of the physics of the problem

T. Gernay, 2017

Performance-Based: Why it matters? What can we gain?

7

Realistic fire scenarios

q

0

600

1200

0 60

[°C]

120 180Time [min]

T. Gernay, 2017


8


Robustness and whole building behavior

Cardington fire test, UK, 1997

T. Gernay, 2017


9



Consideration of specific risk associated with the building

Input variable

𝑔 𝐷𝑉 = 𝑝 𝐷𝑉|𝐷𝑀 𝑝 𝐷𝑀|𝐸𝐷𝑃 𝑝 𝐸𝐷𝑃|𝐼𝑀 𝑔 𝐼𝑀 𝑑𝐷𝑀 𝑑𝐸𝐷𝑃 𝑑𝐼𝑀

T. Gernay, 2017


10



Consideration of specific risk associated with the building

Cost effective fire resistance designs

The Shard, London

T. Gernay, 2017

//upload.wikimedia.org/wikipedia/commons/9/9b/Horniman_London_skyline.jpg

//upload.wikimedia.org/wikipedia/commons/9/9b/Horniman_London_skyline.jpg

Research goal: Develop Performance-Based design in SFE

Comprehend the behavior of building materials and structures in fire

Propose models to accurately capture this behavior

Develop numerical tools for structural fire engineering analysis

11T. Gernay, 2017

Example of research project: How to model concrete in fire?

12

Challenges

numerically robust applicable to large structuresmaterial behavior + at elevated temperature

Need

Concrete is one of the most used materials

Its behavior is affected by fire

There was no satisfying model available for concrete at elevated temperature

T. Gernay, 2017

A model for concrete in fire: Theory

13

Plasticity Damage Plastic-damage

Modeling

Traditional plasticity approach

Damage proposed at ambient temperature

Actually concrete exhibits a combination of both

T. Gernay, 2017


14

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

1.00

2.00

-0.00020 -0.00010 0.00000 0.00010 0.00020 0.00030

str

ess [M

Pa]

strain [-]

Model

Ramtani [test 1990]

Tension

Compression

Crack closure

Modeling

Different in tension and in compression

Can handle the shift from one to the other

Essential because of thermal stresses

T. Gernay, 2017


15

Effects of temperature on stress-strain relationships

Compression Tension

-30

-25

-20

-15

-10

-5

0

-0.03-0.025-0.02-0.015-0.01-0.0050

stress [MPa]

strain [-]

Uniaxial behavior in compression

20°C

200°C

400°C

600°C

800°C

0

1

2

3

0 0.0002 0.0004 0.0006 0.0008 0.001

stress [MPa]

strain [-]

Uniaxial behavior in tension

20°C

200°C

400°C

500°C

T. Gernay, 2017

A model for concrete in fire: Implementation

16

To achieve the greatest impact in practice and be useful to the community:

The model is implemented in a Finite Element software

SAFIR®: non linear FE software for modeling structures in fire

Widely available to the SFE community (+200 licensees)

Compatibility is ensured with the different types of FE:

Model formulated in fully triaxial stress (SOLID FE)

Algorithm for solving in plane stress (SHELL FE)

Also a uniaxial formulation (BEAM FE)

X Y

Z

Diamond 2009.a.5 for SAFIR

FILE: joint9p

NODES: 31502

ELEMENTS: 25411

SOLIDS PLOT

FRONTIERS PLOT

CONTOUR PLOT

TEMPERATURE PLOT

TIME: 120 sec154.40

141.95

129.49

117.04

104.58

92.13

79.67

67.22

54.76

42.31

29.85

17.40

T. Gernay, 2017

A model for concrete in fire: Validation

17

At the material scale

ft

0.0

1.0

2.0

3.0

4.0

0.00 0.02 0.03 0.05 0.06

Str

ess [

MP

a]

Strain [%]

Gopalaratnam [test]

Model

Uniaxial tension

Softening

Stiffness reduction

Permanent strains

Axial strain

Volumetric strain

-40

-30

-20

-10

0

-0.50-0.40-0.30-0.20-0.100.000.10

Str

ess [M

Pa]

Strain [%]

Kupfer et al. [test 1969]

Model

Uniaxial compression

Post-peak

Dilatancy

T. Gernay, 2017


18

At the structural scale

Reinforced concrete slab in fire

Slab 4.30m x 3.30m

Applied load 3.0 kN/m²

ISO fire during 180 minutes

from Lim et al., Eng. Struct. (2004)

T. Gernay, 2017


19


Reinforced concrete slab in fire: Thermal model

0

200

400

600

800

1000

1200

0 30 60 90 120 150 180

Tem

pera

ture

[C

]

Time [min]

Heated surface

55 mm depth

Unheated surface

SAFIR heated surface

SAFIR 55 mm

SAFIR unheated surface

T. Gernay, 2017


20


Reinforced concrete slab in fire: Mechanical model

XY

Z

5.0 E-01 m


FILE: dalle_etc

NODES: 484

BEAMS: 0

TRUSSES: 0

SHELLS: 441

SOILS: 0

DISTRIBUTED LOADS PLOT

DISPLACEMENT PLOT ( x 2)

TIME: 3596 sec

-350

-300

-250

-200

-150

-100

-50

0

0 30 60 90 120 150 180

Ce

ntr

al d

efl

ecti

on

[m

m]

Time [min]

Test data [Lim et al. 2004]

Model

T. Gernay, 2017

• Compartment 15m x 9m

• Composite structure with cellular steel beams

• Two central steel beams are unprotected

• Mechanical load: 3.25 kN/m²

• Fire load: 700 MJ/m² (wood cribs)

21

European project to investigate tensile membrane action

A model for concrete in fire: Simulation of a large-scale fire test

T. Gernay, 2017

22


T. Gernay, 2017

23


T. Gernay, 2017

1. Fire model to get the gas temperature evolution in the compartment

2. Thermal analysis of the sections of the structural components

3. Structural analysis of the composite floor and beams system

24

0

200

400

600

800

1000

1200

0 20 40 60 80 100 120 140 160

Tem

pera

ture

[°C

]

Time [min]

Middle

Lef t bottom corner

Lef t top corner

Right bottom corner

Right top corner

OZone model

111 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 1 1

11

111

11 11 1111 11111 1

11

11

11

11

1 11111

111

1 11 11 111 11 11 11 11 11 11 11 11 11 11 11 11 11 11 111 111 1

1 11 1 1 1

1 11 1

1 1

1

1

1

1

1

2

1

2

1

2

1

2

1

2

1

2

1

2

1

2

1

2

1

22

11

2222222222222222222

1

2

1

2

1

2

1

2

1

2

1

2

1

2

1

2

1

2

1

2

X

Y

Z


FILE: unpr1

NODES: 793

ELEMENTS: 683

FRONTIERS PLOT

CONTOUR PLOT

TEMPERATURE PLOT

TIME: 3600 sec848.90

747.33

645.75

544.18

442.60

341.03

239.45

137.88

36.30

F0

F0

F0 F0

F0

F0

F0

F0 F0

F0

F0

F0

F0 F0

F0

F0

F0

F0

F0

F0

F0

F0

F0

F0 F0

F0

F0F0

F0

F0 F0

F0

F0F0

F0

F0

F0F0

F0

F0 F0

F0

F0F0

F0

F0 F0

F0

F0F0

F0

F0

F0F0

F0

F0 F0

F0

F0

F0 F0

F0

F0

F0

F0

F0 F0

F0

F0

F0 F0

F0

F0

F0

F0

F0 F0

F0

F0

F0 F0

F0

F0

F0

F0

F0 F0

F0

F0

F0 F0

F0

F0

F0

F0

F0 F0

F0

F0

F0 F0

F0

F0

F0

F0

F0 F0

F0

F0

F0 F0

F0

F0

F0

F0

F0 F0

F0

F0

F0

F0 F0

F0

F0

F0

F0

F0

F0

F0

F0

F0

F0 F0

F0

F0

F0

F0 F0

F0

F0

F0

F0 F0

F0

X Y

Z


FILE: UlsterH1

NODES: 2031

BEAMS: 260

TRUSSES: 0

SHELLS: 1664

SOILS: 0

BEAMS PLOT

SHELLS PLOT

IMPOSED DOF PLOT

prot1.tem

prot2.tem

prot3.tem

unpr1.tem

slab_side.tsh

slab_center.tsh

1 2

3


T. Gernay, 2017

25

F0

F0

F0F0

F0

F0

F0

F0F0

F0

F0

F0

F0F0

F0

F0

F0

F0

F0

F0

F0

F0

F0

F0F0

F0

F0 F0

F0

F0F0

F0

F0 F0

F0

F0

F0 F0

F0

F0F0

F0

F0 F0

F0

F0F0

F0

F0 F0

F0

F0

F0 F0

F0

F0F0

F0

F0

F0F0

F0

F0

F0

F0

F0F0

F0

F0

F0F0

F0

F0

F0

F0

F0F0

F0

F0

F0F0

F0

F0

F0

F0

F0F0

F0

F0

F0F0

F0

F0

F0

F0

F0F0

F0

F0

F0F0

F0

F0

F0

F0

F0F0

F0

F0

F0F0

F0

F0

F0

F0

F0F0

F0

F0

F0

F0F0

F0

F0

F0

F0

F0

F0

F0

F0

F0

F0F0

F0

F0

F0

F0F0

F0

F0

F0

F0F0

F0

XY

Z

1.0 E+00 m


FILE: ulsterft1b

NODES: 2031

BEAMS: 260

TRUSSES: 0

SHELLS: 1664

SOILS: 0

SOLIDS: 0

IMPOSED DOF PLOT



N1-N2 MEMBRANE FORCE PLOT

TIME: 3603.4 sec

- Membrane Force

+ Membrane Force

Results

Evolution of the vertical deflection Deflected shape and forces


T. Gernay, 2017

A model for concrete in fire: Implications for the field

Example: composite building design taking advantage of tensile membrane action

26

Protect all elements individually

Performance-based design

40-55% of steel beams can be left unprotected

Prescriptive design

The target performance (stability) can be achieved with the PBD

→ significant cost reduction

→ but to demonstrate it, advanced analysis tools are needed

T. Gernay, 2017

Conclusion

27

Performance based design in Structural Fire Engineering

Challenge: not a simple recipe… but a physically-based, specific solution

Opportunities: flexibility, efficiency and cost reduction for safe design

To understand the physics: models and numerical methods are crucial

New concrete model

For multiaxial stress states and elevated temperature

Successfully applied in a large range of applications

Impact

Better understanding of the behavior of materials and structures

Enables advanced analyses of structures in fire for innovative solutions

Implemented in SAFIR® thus available to the SFE community

T. Gernay, 2017

References

28

Concrete constitutive model

Gernay, T., Franssen, J.-M. (2012). “A formulation of the Eurocode 2 concrete model at elevated temperature that includes an explicit term for transient creep”. Fire Safety J, 51, 1-9.

Gernay T., Millard A., Franssen J.M. (2013). “A multiaxial constitutive model for concrete in the fire situation: Theoretical formulation”. Int J Solids Struct, 50(22-23), 3659-3673.

Gernay, T., & Franssen, J.-M. (2015). “A plastic-damage model for concrete in fire: Applications in structural fire engineering”. Fire Safety J, 71, 268–278.

SAFIR® software

Franssen, J.-M., Gernay, T. (2017). “Modeling structures in fire with SAFIR®: Theoretical background and capabilities”. Journal of Structural Fire Engineering, 8(3).

Fire tests simulated

Lim, L., Buchanan, A., Moss, P., Franssen, J.-M. (2004). “Numerical modelling of two-way reinforced concrete slabs in fire”. Engineering Structures, 26, 1081-1091.

Vassart, O., Bailey, C. G., Hawes, M., Nadjai, A., Simms, W. I., Zhao, B., Gernay, T., Franssen, J.-M. (2012). “Large-scale fire test of unprotected cellular beam acting in membrane action”. Proc. ICE: Structures and Buildings, 165(7), 327–334.

T. Gernay, 2017

Thank you !

Performance-Based Fire Safety Engineering: Challenges and Opportunities

Dr. Thomas Gernay

Gustave Magnel International Award – New activities

SECO – Brussels, Belgium, 1st June 2017

F.R.S.-FNRS, University of Liege, Belgium

performance-based fire safety engineering: … · performance-based fire safety engineering:...

Documents