Concrete filled steel tubular (CFT) columns have become popular as structural member used for buildings. In this paper, theoretical studies are presented on the prediction of bending strength of a concrete filled rectangular tube subjected to uni-axial or bi-axial bending. The main objective of this study is to refine the AIJ design formula which is based on the modified superposed strength method. Bending strength of a column is calculated as the full plastic moment, which is obtained by the generalized-superposed strength method. Proposed formula shows a good agreement with precise numerical solutions.
