Abstract
The ultimate strength of steel beam-columns under biaxial bending is investigated numerically by an elasto-plastic finite displacement analysis considering characteristic values of the measured initial imperfections. And the appropriate interaction strength formulae for beam-columns which are modified from Chen's interaction formula are proposed for the members with box section and I-section, respectively. The proposed formulae are verified by the comparison between the prescribed results and the experimental data. The efficiency of the proposed formulae is demonstrated by the comparisons of several existing design codes.
