Corso di Progettazione Strutturale Antincendio A.A.2022/23. Un esempio completo di analisi prestazionale di una struttura soggetta a incendio.

1. Esempio di struttura
soggetta a incendio: hangar
Prof. Ing. Franco Bontempi
Ordinario di Tecnica delle Costruzioni
Facolta’ di Ingegneria Civile e Industriale
Universita’ degli Studi di Roma “La Sapienza”
franco.bontempi@uniroma1.it

2. 3.6.1.5.4. Verifiche di resistenza
2
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3. Mechanical Analysis
• The mechanical analysis shall be performed for
the same duration as used in the temperature
analysis.
• Verification of fire resistance should be in:
– in the strength domain: Rfi,d,t ≥ Efi,requ,t
(resistance at time t ≥ load effects at time t);
– in the time domain: tfi,d ≥ tfi,requ
(design value of time fire resistance ≥ time required)
– In the temperature domain: Td ≤ Tcr
(design value of the material temperature ≤ critical
material temperature);
3
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4. Verification of fire resistance (3D)
R = structural resistance
T = temperature
t = time
T=T(t)
R=R(t,T)=R(t,T(t))=R(t)
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5. Verification of fire resistance (R-safe)
R = structural resistance
T = temperature
t = time
Rfi,d,t
Efi,requ,t
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6. Verification of fire resistance (R-fail)
R = structural resistance
T = temperature
t = time
Efi,requ,t
Rfi,d,t
Failure !
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7. Verification of fire resistance (t)
R = structural resistance
T = temperature
t = time
Efi,requ,t
Rfi,d,t
Failure !
tfi,d ≥ tfi,requ
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8. 0
200
400
600
800
1000
1200
0 20 40 60 80 100 120
R60 945 ̊C
R30 842 ̊C
R15 739 ̊C R60 945 ̊C
R30 842 ̊C
R15 739 ̊C R90 1006 ̊C
Time [min]
R120 1049 ̊C
8
Standard (Conventional) Fire: ISO 834
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9. R = structural resistance
T = temperature
t = time
Efi,requ,t
Rfi,d,t
Failure !
Td ≤ Tcr
9
Verification of fire resistance (T)
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10. 32,85 m
65,64
m
Vista A-A
Vista B-B
C
C
Vista A-A
Vista B-B
Sezione C-C
32,82 m 32,82 m
7,00 m
12,82
m
9,02
m
16,425 m
Geometry
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11. 11
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12. Structural modelling (1)
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13. Structural modelling (2)
13
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14. Performance goal
1 2 3
4
- ….
- ….
- Structural strength for 20 minutes
- ….
- ….
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15. FIRE MODEL
HEAT TRANSFER
MODEL
STRUCTURAL
MODEL
Fire thermal exposure
Thermal gradients
Load capacity
Room geometry,
Fuel load,
Fire characteristics
Element geometry,
Thermal properties,
Heat transfer coefficients
Element geometry,
Applied loads,
Mechanical properties
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16. Fire modeling: conventional
Curva standard ISO 834
0
100
200
300
400
500
600
700
800
900
1000
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
t (sec)
T
(°C)
7,00 m
6,54m
Fire zone size : 45,8 m2
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17. Constitutive law for steel
Tensioni-Deformazioni al variare della Temperatura
0
50000
100000
150000
200000
250000
300000
0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16 0,18 0,2
Deformazioni (%)
Tensioni
(KN/m
2
)
1100°C
1000°C
900°C
800°C
700°C
600°C
500°C
400°C
300°C
200°C
100°C
Fattori riduttivi delle caratteristiche meccaniche
0,0
0,2
0,4
0,6
0,8
1,0
1,2
0 100 200 300 400 500 600 700 800 900 1000 1100 1200
T (°C)
Fattori
riduttivi
Ky,T
Kp,T
K E,T
T (°C) E (Pa) σy (Pa) α (1/°C)
0 210000000000 235000000 0,00001170
20 210000000000 235000000 0,00001170
100 210000000000 235000000 0,00001195
200 189000000000 232884193 0,00001227
300 168000000000 230689179 0,00001258
400 147000000000 228405976 0,00001297
500 126000000000 178561976 0,00001313
600 65100000000 107131683 0,00001338
700 27300000000 52248249 0,00001360
800 18900000000 25174565 0,00001382
900 14175000000 13851676 0,00001401
1000 9450000000 9234450,5 0,00001419
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18. 2° Scenario
3° Scenario
1° Scenario
Definition of scenarios
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19. 7,00 m
6,54 m
1st Scenario
19
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20. 20
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21. 1st
21
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22. 1st
22
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23. 1st
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24. 1st - lateral displacements
24
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25. 1st - vertical displacements
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26. 7,00 m
2nd Scenario
26
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27. 27
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28. 2nd
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29. 2nd – vertical displacements
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30. 3rd Scenario
30
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31. 3rd
31
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32. 3rd
32
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33. 3rd – vertical displacements
33
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34. 3rd – lateral displacements
34
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35. Scenario 1 Scenario 2 Scenario 3
RESULTS SYNTHESIS
Confronti spostamenti laterali Y
-2,50E-01
-2,00E-01
-1,50E-01
-1,00E-01
-5,00E-02
0,00E+00
5,00E-02
1,00E-01
1,50E-01
2,00E-01
0 1000 2000 3000 4000 5000
Tempo (sec)
Spostamenti
laterali
(m)
Scenaio 3 Scenario 1
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36. FIRE MODEL
HEAT TRANSFER
MODEL
STRUCTURAL
MODEL
Fire thermal exposure
Thermal gradients
Load capacity
Room geometry,
Fuel load,
Fire characteristics
Element geometry,
Thermal properties,
Heat transfer coefficients
Element geometry,
Applied loads,
Mechanical properties
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37. FINITE ELEMENT MODELING
FINITE VOLUME MODELING
FIRE SIMULATION
STRUCTURAL PERFORMANCE
37
Fire modeling: explicit
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38. REAL OBJECT
MODEL
38
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39. 1°Case : NO OPENING
2°Case : OPENING OF THE DOORS AFTER 5 MINUTES DUE
TO FIREFIGTHERS ARRIVE
3°Case : DOORS ALWAYS OPEN
SYSTEM SCENARIOS
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40. 1
2
2
3 3
4
1
2
2
3 3
4
Structure / Action Interaction
Discretization for structural modeling Discretization for action modeling
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41. 41
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42. 2°Case : OPENING OF THE DOORS AFER 5 MINUTES
VENT FIRES
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43. 43
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44. 08/03/2023 PSA - HANGAR 44

45. Ceiling Jet
45
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46. Confronto Zona 1
0
200
400
600
800
1000
1200
0 100 200 300 400 500 600 700 800 900 1000
t(sec)
T(°C)
1° Caso: Ambiente chiuso
2°Caso: Arrivo VVF 5min
3° Caso: Ambiente aperto
1
2
2
3 3
4
1°Case : NO OPENING
2°Case : DOORS OPEN AFTER 5 MNUTES
3°Case : DOORS ALWAYS OPEN
Scenarios Temperatures
46
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47. 0
200
400
600
800
1000
1200
0 100 200 300 400 500 600 700 800 900 1000
t(sec)
T(°C)
ELICOTTERO
CURVA ISO834
CURVA IDROCARBURI
0
200
400
600
800
1000
1200
0 100 200 300 400 500 600 700 800 900 1000
t(sec)
T(°C)
CURVA ISO834
CURVA IDROCARBURI
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48. Esempio di struttura
soggetta a incendio: hangar
Prof. Ing. Franco Bontempi
Ordinario di Tecnica delle Costruzioni
Facolta’ di Ingegneria Civile e Industriale
Universita’ degli Studi di Roma “La Sapienza”
franco.bontempi@uniroma1.it