Kodur and Mackinnon 2000
Experimental Study, Results, and Discussion
Fifty-eight concrete-filled tubular HSS columns were tested to failure through fire exposure. The specimens varied in cross sectional shape (square vs. circle), and varied in concrete fill type (plain concrete, bar-reinforced concrete, and steel-fibre reinforced concrete), and none of the specimens had any fire coating. 55 of the specimens were loaded concentrically, while three were loaded eccentrically. A furnace was used to conduct the fire test, which followed the time-temperature curve of ASTM E119-88 or ULC S101-89. The fire resistance for the bar-reinforced and fibre-reinforced concrete was much higher, and reached 180 minutes, however the plain concrete was only 60-120 minutes. The majority of the plain concrete columns failed by buckling, which occurred with cross-sectional dimensions smaller than 8 in. The results show that the columns expand towards the beginning, however contracted and failed due to load and thermal expansion.
Numerical models were also developed for the various concrete types, which incorporated stress-strain relationships and thermal relationships. The results were compared to and verified by the experimental results. The factors influencing fire resistance were outside diameter, shape of the steel, steel thickness, effective column length, concrete strength, and type of concrete aggregate. For bar reinforced concrete, two additional parameters were included: percentage of bar-reinforcement, and concrete cover for bar reinforcement. Equations were developed for the fire resistance with the parameters above.
Kodur, V. R., Mackinnon, D. H.(2000). “Design of concrete-filled hollow structural steel columns for fire endurance.” National Research Council Canada.