RESISTANCE OF CONCRETE-FILLED, FIRE-RESISTANT STEEL-TUBE COLUMNS

This paper presents experimental results of full-scale fire tests with loading on concrete-filled steel-tube (CFST) columns using fire-resistant (FR)steel for building structural use. By covering the tube surface with protection having lower insulation properties, CFST columns will achieve a superior fire resistance taking advantage of the heat capacity of inner concrete effectively, and they could resist the bending moments caused by eccentric loading without inner reinforcing bars by keeping steel temperature below 600 degrees C. Reinforcing bars are difficult to arrange because inner diaphragms are provided at the beam-column connections against earthquakes in Japan. Fire tests with loading of CFST columns using ordinary steel were also performed for comparison. Aluminum hydroxide calcium carbonate cement-type protection (ceramic protection) and foaming-type intumescent coating were used for the protection material. The fire tests with loading were carried out at the furnace in the General Building Research Corporation, Osaka, Japan.