Experimental and numerical study of fire performance of L-shaped concrete-filled steel tubular columns under eccentric compression

Six special-shaped columns composed of concrete-filled steel tubes (CFST) were designed and tested based on the ISO-834 temperature curve to access their fire performance under eccentric loads. Key test variables include the types of stiffener, load eccentricity, as well as load angle, and the failure modes, temperature distribution, and deformation of specimens were analyzed. The test outcomes indicate that the L-shaped CFST columns’ fire resistance declines as the load eccentricity rises, but its decrease amplitude narrows under a relatively high eccentricity. Besides, the impact exerted by the load angle on the columns’ fire resistance is also significant. A Finite Element Analysis (FEA) method was carried out afterward and compared with the test outcomes. Moreover, an extensive parametric analysis containing 2008 FEA models was developed to study the impact of major parameters on the L-shaped CFST columns’ fire resistance, namely 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), steel strength (f_y), concrete strength (f_ck), and load angle (θ). The analysis results imply that the parameter of load ratio (n) remarkably affects the columns’ fire resistance, while the other parameters exert a certain impact on the fire resistance when n < 0.5. Given the test and analysis, a simplified calculation approach for the fire resistance of L-shaped CFST columns is designed.