The authors propose the elasto-plastic frame analysis on steel frames with composite beams, focusing on the structural non-linearity of headed studs. The structural non-linearity was experimentally investigated while the slip rigidity was theoretically calculated. This analytical method showed a good agreement with the results of tests on steel frames with continuously spanned or long-spanned composite beams, leading to the fact that the effective width of slab on long-spanned beams should be taken shorter than designed, while the one for short-spanned beams may be taken as the same as designed.
