Concentric and eccentric compressive behaviors of stiffened T-shaped CFST columns

Longitudinal stiffeners can improve the mechanical performance of T-shaped concrete-filled steel tubular (CFST) columns. In practical applications, stiffened T-shaped CFST is often subjected to bidirectional loading, but there has been few studies on its concentric and eccentric compressive performance considering different loading angles in the past. Therefore, six stiffened T-shaped CFST columns were tested in this paper and the main pa-rameters were loading angle (45 degrees and 135 degrees), load eccentricity (0, 0.25 and 0.5), and slenderness ratio (31.5 and 41.9). Finite element (FE) models of stiffened T-shaped CFST columns under different loading angles were established, and the practical design methods for concentrically and eccentrically loaded columns were obtained on the basis of parametric analysis. The results show that the ultimate strength of stiffened T-shaped CFST column at 135 degrees is greater than that at 45 degrees with a difference of 12.6%. Setting longitudinal stiffeners can increase the ultimate strength by 13.2%-24.5%, and the enhancement extent declines with increasing load eccentricity. The maximum deviation of loading angles on stability coefficient under different slenderness ratios can reach 33.9%, while the corresponding deviation on relative moment (M/Mu) under different relative axial load (N/Nu) can reach 63.4%. The design method of stability coefficient for multi-cell T-shaped CFST is also available for concentrically loaded stiffened columns. Considering the loading angle transformation, the proposed interaction curve formulas can be used for the design of eccentrically loaded stiffened T-shaped CFST columns with good accuracy.