1. CE 808: Structural Fire Engineering SAFIR - Computer Program
V. Kodur, Professor
Dept of Civil and Env. Engineering
Michigan State University

2. SAFIR - Computer Program
Introduction
Fire Definition
Thermal response
Mechanical response
Material Properties at El. Temp.
Case Studies
CE 808 – Structural Fire Engineering

3. CE 808 – Structural Fire Engineering
Introduction
SAFIR Computer Program
Model the thermo-mechanical behavior of structures exposed to fire
Salient Features
FEM based program
Nonlinearity - geometric & material
Ambient & high temp.
Thermal & structural analysis
University of Liege
Jean-Marc Franssen
CE 808 – Structural Fire Engineering

4. Structural Fire Design: 3 Steps
Fire Growth
(name.fct)
Thermal Analysis
(name.in)
Structural Analysis
Define the fire (user defined)
Calculate the temp. in the structure
Calculate the mechanical behaviour
CE 808 – Structural Fire Engineering

5. CE 808 – Structural Fire Engineering
Fire Definition
Included in SAFIR
ISO 834
ASTM E119
hydrocarbon curve of Eurocode 1
external fire curve of Eurocode 1
Input unique time-temp curve
User defined (name.in)
CE 808 – Structural Fire Engineering

6. Fire Definition Sample Time-Temp. Curve (User defined)
100
200
300
400
500
600
700
800
900
1000
Beginning of Ventilation
Temperature [°C]
controlled fire
OPENING of Vertical Vents 10 20 30 40 50 60 70
Time [min]
Sample Time-Temp. Curve (User defined)
CE 808 – Structural Fire Engineering

7. CE 808 – Structural Fire Engineering
Thermal Analysis
Plane or 3 D sections
Standard or real fire exposure
Varying material properties
Steel
Concrete
Insulation
User
Thermal properties
Member temperatures
CE 808 – Structural Fire Engineering

8. Governing Eqn, Steady Heat Conduction
Transformation of PDE into element equilibrium eqn
K = Material constant
T = temperature
Q = heat flux
CE 808 – Structural Fire Engineering

9. Thermal Response: Discretization
True section
Matching
Discretized section
CE 808 – Structural Fire Engineering

10. Thermal Response: Discretization
2-D & 3-D Element Meshes
CE 808 – Structural Fire Engineering

11. Thermal Response: Discretization
¼ of a 30 cm x 30 cm reinforced concrete section
CE 808 – Structural Fire Engineering

12. Thermal Response: Discretization
Prestressed concrete T-beam
CE 808 – Structural Fire Engineering

13. CE 808 – Structural Fire Engineering
Thermal Response: Discretization
Concrete Filled Steel Section (courtesy NRCC)
CE 808 – Structural Fire Engineering

14. Material Properties – TC of Concrete
Non linear thermal properties
2.5
Concrete
Heating
2.0
Cooling
1.5
Thermal conductivity [W/mK]
1.0
0.5
Temperature [°C]
0.0
200
400
600
800
1000
CE 808 – Structural Fire Engineering

15. Material Properties – Sp. heat of concrete7
Enthalpy [J/cm³K] 6
Specific heat [kJ/kgK] 5 4 3 2 1
200
400
600
800
1000
1200
Temperature [°C]
CE 808 – Structural Fire Engineering

16. Thermal Response: Results
Prestressed concrete section
CE 808 – Structural Fire Engineering

17. Thermal Response: Results (3D)
Steel column through a concrete slab
Composite beam partly heated
CE 808 – Structural Fire Engineering

18. Thermal Response: Results (3D)
Composite steel-concrete joint discretization
CE 808 – Structural Fire Engineering

19. Thermal Response: Results (3D)
Composite steel-concrete joint
surface temperatures
CE 808 – Structural Fire Engineering

20. Thermal Response: Results (3D)
Composite steel-concrete joint
Temperatures on steel elements (concrete is transparent)
CE 808 – Structural Fire Engineering

21. Thermal Response: Results (3D)
Composite steel-concrete joint
Temperatures on concrete elements (steel transparent)
CE 808 – Structural Fire Engineering

22. Thermal Response: Limitations
Free water –evaporation is taken into account, but not migration of moisture
Internal cavities only in 2D sections
Perfect conductive contact between materials
Fixed geometry
No influence of cracking in materials
CE 808 – Structural Fire Engineering

23. CE 808 – Structural Fire Engineering
Structural Analysis
Plane or 3 D sections
Truss, beam, solid, shell
Large displacements
Static & dynamic analysis
Composite sections
Imposed deformation
CE 808 – Structural Fire Engineering

24. Governing Eqn. - Mechanical Response
Integration on section of beam element
CE 808 – Structural Fire Engineering

25. Governing Eqn. - Mechanical Response
E = Elastic Modulus
A = Area
Sy = Y-axis elastic section modulus
Iy = Y-axix moment of inertia
N = Axial load
My = Y-axis bending moment
CE 808 – Structural Fire Engineering

26. Governing Eqn. - Mechanical Response
Element equilibrium equation:
The local equilibrium equation
CE 808 – Structural Fire Engineering

27. Mechanical Calculation: Discretization6 3 1 3 6
Truss
Beam 6 6 3 3 6 6 3 3 3 6 3 6 3 6
Solid
Shell
CE 808 – Structural Fire Engineering

28. Mechanical Calculation: Discretization
Discretization of the beam
CE 808 – Structural Fire Engineering

29. Material Properties - Steel
Stress-strain relationship in steel
CE 808 – Structural Fire Engineering

30. Material Properties - Concrete
0.0
0.2
0.4
0.6
0.8
1.0
0.5
1.5
2.0
2.5
3.0
Stress Related Strain [%]
Stress / Peak Stress at 20°C
20°C
100°C
200°C
300°C
400°C
500°C
600°C
Stress-Strain Relationship, Concrete
CE 808 – Structural Fire Engineering

31. Material Properties - Concrete
0.016
0.014
0.012
0.010
Tmax = 1000
Tmax = 800
0.008
Thermal strain
Tmax = 600
0.006
Tmax = 400
0.004
Tmax = 200
0.002
EC2
0.000
200
400
600
800
1000
1200
-0.002
Temperature [°C]
Thermal expansion of concrete
CE 808 – Structural Fire Engineering

32. CE 808 – Structural Fire Engineering
Mechanical Response - Results
CE 808 – Structural Fire Engineering

33. Mechanical Response - Results
CE 808 – Structural Fire Engineering

34. Mechanical Response - Results
CE 808 – Structural Fire Engineering

35. Mechanical Response - Results
CE 808 – Structural Fire Engineering

36. Mechanical Response - Results
Fire in this
compartment
2D steel frame (courtesy Vila Real & Piloto)
Support conditions and loading
CE 808 – Structural Fire Engineering

37. Mechanical Response - Results
2D steel frame (courtesy Vila Real & Piloto)
Evolution of the displacements
CE 808 – Structural Fire Engineering

38. Mechanical Response - Results
2D steel frame (courtesy Vila Real & Piloto)
Axial forces
CE 808 – Structural Fire Engineering

39. Mechanical Response - Results
2D steel frame (courtesy Vila Real & Piloto)
Flexural forces
CE 808 – Structural Fire Engineering

40. Mechanical Response: Limitations
Spalling not modeled.
No mechanical analysis with solid F. E.
Improvements
plane stress concrete model in the shell.
more robust algorithm for tracking the behavior after local collapse
CE 808 – Structural Fire Engineering

41. CE 808 – Structural Fire Engineering
Input Data
Structure/member dimensions
Discretization details
Fire characteristics
Material properties
Load
Analysis/output options
Fire Growth and Thermal Analysis
Data file 1
Structural Analysis
Data file 2
Output from Thermal Analysis
CE 808 – Structural Fire Engineering

42. CE 808 – Structural Fire Engineering
Output Results
Temperatures
Stresses and strains
Deformations
Fire resistance
Post processor - Diamond
CE 808 – Structural Fire Engineering