In this study, the collapse mode and the plastic deformation capacity of 590N/mm^2 high strength steel beam with scallops connected to box column is investigated by the monotonic loading test and the numerical analysis. And the stress transfer quantity from beam web to column is investigated too. It is clear that this quantity is influenced by column plate thickness greatly and not depend on the web thickness. As a result, if this quantity is small, beam collapses with fracture. Particularly, beam that has thick web plate is easy to collapse with fracture, and the plastic deformation capacity becomes small.
