A study on the behavior of eccentrically compressed square concrete-filled steel tube columns

In this study the bending moment–axial force–curvature (M–N–ΦM–N–Φ) relation for eccentrically compressed square CFT columns is obtained by basic analysis of mechanics which takes into account the effect of residual stress of steel and non-linearity of concrete and steel. This study presents a simplified analytical method for predicting the ultimate strength of eccentrically compressed square concrete filled steel tube (CFT) columns based on the collapse theory. The proposed method can also be used in the prediction of ultimate strength of axially compressed columns with initial imperfections as they are treated as equivalent slightly eccentrically compressed columns. The results obtained by the proposed method agree well with the experiments.