1. New approach for evaluating Equivalent fire severity of Design fires
Purushotham Pakala A
11/20/2018
Purushotham Pakala

2. Outline Introduction Design Vs Standard fire Equivalent Fire Severity
Equal energy method
Simulations & Results
Conclusions
11/20/2018
Purushotham Pakala

3. Introduction Most destructive natural calamity Damage varies (L, P, E)
Proper knowledge of material properties, behavior required
Concrete Vs Steel
11/20/2018
Purushotham Pakala

4. Design Vs Standard fire
Real Vs Ideal
Varies across scenarios
Behavior of structural elements is entirely different
Conditions different
11/20/2018
Purushotham Pakala

5. Equivalent Fire severity
Means of comparison between Design and Real fire
Resistance >= Severity
Equivalent area method
Areas are compared
Maximum Temperature concept
Peak Temperature compared
Minimum load capacity concept ( Deflection)
Max deflection or Min load capacity compared
Empirical formulas
11/20/2018
Purushotham Pakala

6. Pros Vs Cons
Equal area method good for correcting results of erroneous standard-fire resistance tests .No account of heat transfer (short hot vs long cold fire)
Max. Temperature applicable for insulating elements. Inadequate if max temp is more or less than that of standard fire
More realistic concept for load bearing elements
11/20/2018
Purushotham Pakala

7. Equal energy method Heat transfer mostly by radiation and convection.
Technically strong to compare the amount of heat energy released than just comparing areas
11/20/2018
Purushotham Pakala

8. Problem at hand Loading = 16kips/ft L 11/20/2018 Purushotham Pakala
6  20 mm
(a) Cross Section
150 mm
500 mm
300 mm
 10 mm stirrups
40 mm
Loading L
Loading = 16kips/ft
11/20/2018
Purushotham Pakala

9. Fire Scenarios Fire Scenario Fuel Load (MJ/m2 floor area)
Ventilation Factor
(m0.5)
Thermal capacity (Ws0.5/m2K ) 1
1600
0.02
488 2
1200 3
0.04 4
800 5
1900 6 7
400
0.026 8
1100 9
1300
0.03 10
900 11
1000 12
700
0.035 13
11/20/2018
Purushotham Pakala

10. Simulated Design fires (upto 7 hrs)
11/20/2018
Purushotham Pakala

11. Maximum Temperature (C)
Results
Fire Scenario
Maximum Temperature (C) 1
1270.5 2
1229.6 3
1314 4 5
861.3 6 7
717.4 8
1306.4 9
890.4 10
1285.2 11
798.7 12
824.5 13
11/20/2018
Purushotham Pakala

12. Equal Energy concept 11/20/2018 Purushotham Pakala Standard Fire
Design
fires
11/20/2018
Purushotham Pakala

13. Results Time Equivalent (Minutes) Fire Scenario
Maximum Temperature ( C)
Energy Method
Area Method
Deflection method 1
1270.5
309.5
294.1
372.5 2
1229.6
235.6
223.3
280 3
1314
173.9
124.8
170 4
125.4
93.5
135 5
861.3
137.5
232.1
235 6
56.2
74.9
105 7
717.4
36.3
56.9 75 8
1306.4
162.1
117.1
162.5 9
890.4
93.1
132.6 10
1285.2
137.9
101.4
145 11
798.7
83.7
138.9
157.5 12
824.5 52
72.6
102.5 13
11/20/2018
Purushotham Pakala

14. Correlation
11/20/2018
Purushotham Pakala

15. Interpretation and Conclusions
Energy Vs Deflection
Works well for max temp above standard fire (~ 5,6,7,11,12)
Modified Equal Energy Method =
( *Tmax)* Teq (obtained from equal energy method)
Should account for radiative effects in severe, simple fires (max temp)
Compatible with equal area if max temp less than standard fire (5,6,7,11,12)
11/20/2018
Purushotham Pakala

16. Future
Address the effect of radiation in fires where peak temperatures are less.
Various support conditions
Restraints
11/20/2018
Purushotham Pakala

17. Thank You 
11/20/2018
Purushotham Pakala