Abstract
This paper presents an appropriate design formula for steel beam-columns based on the ultimate strength. The strength of beam-columns is evaluated by an elasto-plastic finite displacement analysis considering characteristic values of measured initial imperfections. The strength analysis is carried out for in-plane and out-of-plane failure having welded box section and I-section, respectively. For the design formula of in-plane failure the conventional linear interaction equation is acceptable providing that the column strength used in the equation should be given appropriately. On the other hand, in the case of out-of-plane failure a non-linear interaction equation is proposed. It is made clear that the resistance factor for columns and beams can also be adopted effectively to those for beam-columns according to the SGST-format. Finally, the proposed formula is verified by the comparison between the prescribed results and the experimental data.
