It is crucial to establish method evaluating ductility demand of beams for seismic design of structures. However, there are few studies on the demand of haunched beams and reduced section beam (internal plastic hinge beams) in steel moment resisting frames subjected to severe earthquakes. This paper proposes a damage prediction method of internal hinge beams based on energy equilibrium, and confirms applicability of the method. By applying the proposed method, the difference in damage between internal hinge beams and ordinary beams has been quantitatively clarified, and it can be concluded that the ductility demand of the former beams is not more than the the demand for the latter beams.
