Theoretical studies are presented on the prediction of bending strength of a composite beam-column subjected to bi-directional bending. The term bi-directional bending is defined as the bending where the both ends of a bar are subjected to end moments of differnt directions. The main objective of this study is to refine the AIJ design formula which is based on the modified-superposed strength method. Strength of a composite beam-column, subjected to bi-directional bending, is obtained as the smaller value between the biaxial short column strength of the critical end section and that of the approximate solution of collapse at the mid-span. Proposed formula shows a good agreement with precise numerical solutions and/or experimental results.
