Fire resistance of double-skinned composite tubular columns including concrete confinement

Double-skinned composite tubular (DSCT) columns consisting of concrete cast between outer and inner tubes have been developed to overcome certain limitations of other columns, such as the large self-weight of concrete-filled tubular columns and lack of concrete confinement of hollow concrete-filled tubular columns. The strength and ductility of the column are enhanced by the continuous confining stress provided by the inner tube. Their excellent structural performances make them particularly suitable for applications in high-rise buildings. However, if a high-rise building is damaged by fire, the economic costs associated with building repair can be high. It is very important to put the fire-damaged building back into service with the minimum post-fire repair. Thus, to predict the status of a structure under fire, its behavior should be evaluated based on the fire duration. Studies on the fire resistance of DSCT columns have been carried out for this purpose. However, they have involved the performance of the entire system without considering the effects of the DSCT column’s components on the fire resistance. In this paper, the behavior of a DSCT column is investigated under an ISO-834 standard fire using an analytical method. The evaluation method for the fire resistance of a DSCT column utilizes a thermal analysis and Eurocode. In addition, the relationship between the DSCT column’s components and the fire resistance is investigated, considering the confining effect. Moreover, the behavior of the DSCT column is evaluated through parametric studies of the hollow ratio, thickness of the outer tube, and thickness of the inner tube.