Fire behaviour of thin-walled steel tube confined reinforced concrete stub columns under axial compression

Thin-walled steel tube confined reinforced concrete columns are new-type composite members and the static and seismic performance of these columns have been extensively investigated in recent decades. There are, however, very limited studies on the fire behaviour of the steel tube confined reinforced concrete stub columns subjected to axial compression. In this paper, experimental and numerical studies on the fire response of steel tube confined reinforced concrete stub columns under axial compression are presented. A total of eight specimens with varying wall thicknesses of steel tube and load ratios were tested to failure under the ISO-834 standard fire. Temperature distribution, axial deformation, failure modes, and fire duration were recorded in the fire tests. Finite element (FE) models were established using ABAQUS to estimate the fire behaviour and the models were validated by comparing with the measured results. Parametric studies were then performed on the fire resistance of thin-walled steel tube confined reinforced concrete stub columns and the considered parameters include diameter of steel tube, wall thickness of steel tube, load ratio, reinforcement ratio, material strength, and concrete cover thickness. The studies show that the load ratio and diameter of steel tube are two key factors governing fire resistance of thin-walled steel tube confined reinforced concrete stub columns. Based on test and numerical results, a design approach was proposed to predict the temperature distribution and loading capacity of thin-walled steel tube confined reinforced concrete stub columns under ISO-834 standard fire.