Performance of steel reinforced concrete columns after exposure to fire: Numerical analysis and application

One advantage of steel reinforced concrete (SRC) columns is that the concrete encasement reduces the maximum temperature attained by the steel section in the full-range fire situation. For fire-exposed SRC columns, a better understanding of their post-fire performance can facilitate their rehabilitation and being re-used. This paper presents a numerical study into the post-fire performance of SRC columns. Results show that an SRC column of 600 x 600 mm in cross-section retained 0.87 times of the original load-bearing capacity after exposure to full-range fire with a heating duration of 45 min and a subsequent linear cooling down phase of 139 min. After the SRC column fully cooled down to ambient temperature, the proportion of load carried by the steel section increased to 73%, significantly higher than the level at ambient temperature (20%). Results of the parametric study revealed that a number of factors, i.e., duration of fire exposure, cross-sectional size, slenderness ratio and concrete strength, significantly affected the post-fire residual strength. The numerical method was applied to the post-fire assessment of the SRC columns in a fire-exposed building and a case study is presented. The resistance of the SRC column to compression reduced by 4% after fire exposure. By using the proposed repair method, the resistance to compression can be recovered by 11% compared to that before fire exposure.