TESTS ON THE RESIDUAL STRENGTH OF CONCRETE FILLED STEEL TUBULAR COLUMNS AFTER EXPOSURE TO FIRE

The behavior of concrete filled steel tubular columns subjected to axial or eccentric loads was experimentally investigated. Both protected and unprotected concrete filled steel tubular columns were tested and the results are presented in this paper. The fire attacks in the test are those prescribed in the ISO-834 and the China National Standard GB-9978. The tested specimens included six circular columns and six square columns. It was found that the loss of the strength of unprotected specimens is significantly greater than that of protected columns. The slenderness ratio has a significant influence on the strength loss ratio, and large loss of strength is expected for specimens with large slenderness ratios. It was also observed that the load eccentricity ratio has little influence on the strength loss ratio. The results in this paper may serve as a reference for practical design.