Fire safety design method of circular steel tube confined reinforced concrete columns

To date, few research has been reported on the fire behavior of steel tube confined reinforced concrete (STCRC) columns and there is no available fire safety design method for this kind of column. Fire safety design methods for reinforced concrete (RC) columns and concrete-filled steel tubular (CFST) columns are generally employed for STCRC columns in practice. However, fire resistance of STCRC column differs from those of RC column and CFST column owning to their different behaviors. A method for predicting fire resistance of circular STCRC column was proposed. Influences of parameters, including load ratio, slenderness ratio, etc., on the fire resistance were analyzed. Fire resistance of circular STCRC columns was compared with those of RC columns and CFST columns. It can be found that the load ratio has a significant influence on the fire resistance, as the fire resistance decreases with the increase of load ratio. Parameters including slenderness ratio, cross-section dimension, etc., have obvious influences on fire resistance of columns with low load ratios. Fire resistance of the circular STCRC column is 14.4%-66.0% of that of the RC column, and the difference grows with increase of load ratio, which means that it is unsafe to design circular STCRC columns following methods for RC columns. Compared with the CFST column, the circular STCRC column possesses higher fire resistance, which can be 1.0-3.0 times of that of the CFST column.