Buckling Strength of Slender Reinforced HSC and VHSC Columns in Fire

Abstract

In fire, it is anticipated that slender RC columns would be more vulnerable to buckling failure than to cross sectional failure because of thermal degradation in the cover concrete. This paper presents the main results from an experimental and analytical study of this phenomenon in slender RC columns using high-strength concrete (HSC) and very high-strength concrete (VHSC) under fire conditions. The parameters in the fire resistance tests were concrete strength, cross-sectional shape, axial force and the ratio of column height to cross-sectional diameter, and we consequently obtained fire-resistance time and failure mode. For analysis, a finiteelement method with an assumption of the Bernoulli-Euler theory was applied. The analysis, using a method proposed by the authors based on tangent-modulus theory, evaluates the buckling strength under fire conditions. A comparison of the experimental and analytical results shows that the proposed analysis method offers a good approximation of both fire-resistance time and failure mode.