Neno Toric

COST Action TU0904
Integrated Fire Engineering and Response
Training school
University of Malta, Sliema, 11.-14. April 2012.
Scientific project: Reliability of Structures and Risk Assesment to Extreme
Loading, Ministry of Science and Tehnology, Croatia
NEW NUMERICAL MODELS FOR
BEHAVIOUR OF STEEL AND CONCRETE
STRUCTURES EXPOSED TO FIRE
Neno Torić, PhD student
UNIVERSITY OF SPLIT, CROATIA
FACULTY OF CIVIL ENGINEERING, ARCHITECTURE AND GEODESY
Chair for steel and timber structures

• Introduction
• Research concept
OVERVIEW
• Numerical model for behaviour of steel and concrete structures
exposed to fire
• Experimental research
• Numerical examples
• Discussion

INTRODUCTION
• Development of structural analysis models for predicting fire behaviour
• Current research is focused on development of structural analysis model
comprised of 3D heat transfer model, model for calculating mechanical
properties of the cross section and model for structural analysis
• Development of simplifed model for calculating mechanical properties of the
cross section taking into account the additional load dependent strains that
occur during heating (creep, transient-creep)
• Calculation of modified stress-strain curves which implicitly take into
account the additional load dependent strains (strain modified curves)
3

RESEARCH CONCEPT
Steel – steady state test vs. transient state test vs. EC3
steady-state test EC3
transient-state test
4

Stress [MPa]
70
60
50
40
30
20
10
0
RESEARCH CONCEPT
Concrete – steady state test vs. EC2
0 0.004 0.008 0.012
Strain
0.016 0.02 0.024
EN1992-1-2 - 20°C
EN1992-1-2] - 230°C
EN1992-1-2 - 400°C
EN1992-1-2 - 500°C
EN1992-1-2 - 600°C
EN1992-1-2 - 700°C
EN1992-1-2 - 800°C
STEADY S. TEST - 20°C
STEADY S. TEST - 230°C
STEADY S. TEST - 400°C
STEADY S. TEST - 500°C
STEADY S. TEST - 600°C
STEADY S. TEST - 700°C
STEADY S. TEST - 800°C
5

RESEARCH CONCEPT
• Strain modified curve
6

NUMERICAL MODEL FOR BEHAVIOUR OF STEEL
AND CONCRETE STRUCTURES EXPOSED TO FIRE
3D Bernoulli beam
(6 D.O.F.)
• 3D nonlinear heat transfer model,
• Model for calculating mechanical properties of the cross section
• Model for structural analysis
Cross-section discretization
6
5
1
3
(0,0,0)
2
7
2 3
7
1
3D Cube element
8
4

NUMERICAL MODEL FOR BEHAVIOUR OF STEEL
AND CONCRETE STRUCTURES EXPOSED TO FIRE
• Calculation procedure for strain modified curve
8

EXPERIMENTAL RESEARCH
• Material behaviour
9

EXPERIMENTAL RESEARCH
• Structure behaviour
Furnace
625 1250 625
V
V
2500
Furnace
625 1250 625
V
V
2500
H
H
V
10
V

EXPERIMENTAL RESEARCH
• Structure behaviour
Chimney
lvdt3
lvdt4
8280
2730 2820 2730
aerated concrete blocks
HE 320 A
H1 H1
4145 4140
2730 2820 2730
12 13 14
oil burner
oil burner oil burner
HE 200 A
11
1955
1590
255
3800

Creep model:
Dorn/Harmathy
NUMERICAL EXAMPLES
Example 1
V
Furnace
625 1250 625
V
2500
V=200 kN
Steel: S355
V
12

NUMERICAL EXAMPLES
Example 1
13

NUMERICAL EXAMPLES
Example 1
14

NUMERICAL EXAMPLES
Example 1
15

Temperature [°C]
600
500
400
300
200
100
0
NUMERICAL EXAMPLES
Example 1
0 10 20 30 40 50 60 70 80 90 100 110
Ti m e [m i n ]
T_furnace
Exp upper flange
Exp lower flange 3
Model
16

Midspan deflection [mm]
50
45
40
35
30
25
20
15
10
5
0
NUMERICAL EXAMPLES
Exp midspan defl
EC3
Example 1
Exp stress-strain curves without creep
Exp strain modified curves
EC3 strain modified curves
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115
Time [min]
17

Creep model:
Dorn/Harmathy
NUMERICAL EXAMPLES
V
Example 2
Furnace
625 1250 625
V
2500
V=200 kN
H=400 kN
Steel: S355
H
H
V
18

NUMERICAL EXAMPLES
Example 2
19

NUMERICAL EXAMPLES
Example 2
20

NUMERICAL EXAMPLES
Example 2
21

Temperature [°C]
550
500
450
400
350
300
250
200
150
100
50
0
NUMERICAL EXAMPLES
T_furnace
Exp upper flange
Exp lower flange
Model
Example 2
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190
Time [min]
22

Midspan deflection [mm]
60
50
40
30
20
10
0
Exp midspan defl
EC3
NUMERICAL EXAMPLES
Exp stress-strain curves without creep
EC3 strain modified curves
Exp strain modified curves
Example 2
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190
Time [min]
23

NUMERICAL EXAMPLES
Transient-creep model:
Anderberg/Thelandersson
Example 3
K K
K K
2730 2820 2730
8280
d=20 cm
K=20 kN
Concrete: C 60/70
Prest. Steel - fy=1600 MPa
24

NUMERICAL EXAMPLES
Example 3
25

NUMERICAL EXAMPLES
Example 3
26

NUMERICAL EXAMPLES
Example 3
27

Temperature [°C]
1000
900
800
700
600
500
400
300
200
100
0
NUMERICAL EXAMPLES
Example 3
Exp cable T7
Exp cable T8
Exp cable T9
Exp void T10
Exp surface T11
Model T7
Model T8,T9
Model T10
Model T11
T_furnace
0 10 20 30 40
Time [min]
50 60 70 80
28

Deflection (mm)
220
200
180
160
140
120
100
80
60
40
20
0
-20
Exp midspan defl LVDT3
Exp midspan defl LVDT4
Exp stress-strain curves
EC2
Exp strain modified curves
EC2 strain modified curves
NUMERICAL EXAMPLES
Example 3
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
Time (min)
29

DISCUSSION
• Application of strain modifed curves in classical structural analysis
calculation was presented
• Validity of the strain modified curves was tested on results of three different
experiments conducted on testing of simply supported steel and
prestressed concrete elements exposed to high temperatures
• Numerical results of the three presented examples show good agreement
with the experiment by using strain modified curves in terms of predicting
the structural stiffness
• Further research is required to confirm the application of the presented
calculation methodology
30

THANK YOU FOR YOUR
ATTENTION