Fire resistance of T-shaped concrete-filled steel tubular columns under eccentric compression

In order to study the fire resistance of T-shaped concrete-filled steel tubular (CFST) columns subjected to eccentric loading, a series of fire tests were conducted along with a numerical study. Specifically, six half-scaled T-shaped CFST columns were tested under the ISO-834 standard fire; and the parameters of stiffener type, load eccentricity, and load angle were considered. The failure modes, thermal response, and structural response were investigated. The test results show that the fire resistance of T-shaped CFST columns decreases with the increase of load eccentricity, but at a lesser degree for relatively high eccentricity. The load angle also has a significant influence on the fire resistance of the columns. A finite element (FE) analysis was then conducted to establish the temperature field model and the thermo-mechanical coupling model which were both validated by the test results. Furthermore, an extensive parametric study including 2008 FE analyses was carried out to investigate the effects of key parameters on the fire resistance of T-shaped CFST columns, including load ratio (n), slenderness ratio (λ), column limb width (B), column limb depth-to-width ratio (D/B), load eccentricity ratio (e/r₀), steel ratio (α_s), material strength (f_y and f_ck), and load angle (θ). The parametric study indicates that the load ratio n has a significant effect on the fire resistance of T-shaped CFST columns and the other parameters also have certain influences on the fire resistance when n < 0.5. Based on the numerical studies, a simplified method to calculate the fire resistance of T-shaped CFST columns is proposed.