Performance of square steel-reinforced concrete-filled steel tubular columns subject to non-uniform fire

Abstract Fire design guidance for composite columns is based on the performance of these columns when heated uniformly along their lengths. However, it is important to understand the behaviour of these columns when heated non-uniformly as this constitutes a more practicable representation. Here, the performance of square steel-reinforced concrete-filled steel tubular (SRCFST) columns was tested under 4-sided, 3-sided, 2-sided and 1-sided fires. Six columns were 1.8 m in height with pinned-fixed boundary condition. The fire resistance of SRCFST columns under 4-sided and 3-sided fires exposure was found to be similar in the experimental tests and their failure modes significantly different. SRCFT columns under 2-sided and 1-sided fires performed better than expected as these did not reach failure before 240 min. The results are used to validate a non-linear elastic-plastic finite element model. Validated numerical and experimental results are compared with available advanced prediction methods. It is shown that none of these is capable of providing accurate fire resistance prediction for SRCFST columns under uniform or non-uniform fire.