1. The effect of varying fire scenarios on fire resistance ratings of reinforced concrete columns
Khaled Sharawi
CE 808

2. Summary Characteristics of Concrete Spalling Design Methods
Analysis of Reinforced Concrete columns
Results
Conclusion
Celebration

3. Characteristics of Concrete
Non-combustible material and retains high percentage of strength at elevated temperatures.
Low thermal diffusivity and conductivity.
Resists heat transmission
The modulus of elasticity and shear modulus decrease with the increase of temperature.
Great fire endurance
No additional costs for fire proofing

4. Characteristics of Concrete

5. Spalling
Spalling occurs when water vapor is driven off from the cement paste during heating, with high pore pressures creating large tensile stresses greater than the tensile strength of the concrete.
There are several different types of spalling including: Surface spalling, corner spalling, aggregate spalling and explosive spalling.
Prevention: The addition of fine polypropylene fibers to the concrete mix. These fibers decrease the probability of spalling because the polypropylene melts during fire exposure, increasing the porosity by leaving cavities through which water vapor can escape.

6. Design Methods
ACI
Euro code
Australian Method
Dr. Kodur

7. Analysis Characteristics of the column: 300mm x 300mm
Area of Steel = 400mm2
Number of rebars = 4

8. Analysis
The square column will be tested for 1, 2, 3, and 4 face fire exposure to determine the effect of the different fire scenarios on the fire rating of the column.

9. 4 face exposure
Use symmetry
30 mm cover

10. 4 face exposure

11. 4 face exposure
40 mm cover

12. 4 face exposure

13. 3 face exposure

14. 3 face exposure

15. 2 face exposure

16. 2 face exposure

17. 1 face exposure

18. 1 face exposure

19. Summary of Results Fire Scenario Cover (mm) Time to failure (s)
Fire Rating (hr)
4 faced 30
4000 = 66.7 min 1 40
6750 = min
1.5
3 faced
4500 = 75 min
2 faced
4250 = 70 min
1 faced
6250 = 104 min

20. Conclusion Greater concrete cover results in higher resistance rating.
The temperature in the reinforcing bars is the critical failing temperature. Usually around 550C.
Different fire scenarios change the fire rating of a section.
4 faced fire exposure gives the least fire rating.
1 faced fire exposure gives the highest fire rating.
The shape of an element, whether square or circular, does not prevent the occurrence of spalling.
The diameter of reinforcement has no influence on surface spalling.
Reinforcement closest to fire side reaches failure first.

21. Conclusion 2 3 3 2 1 2 2 1 1= Highest Exposure 2= Medium Exposure
1= Highest Exposure
2= Medium Exposure
3= Least Exposure

22. Questions???

23. Celebrate!!!!!