This paper deals with steel frames in which hysteretic dampers are incorporated and examines the strength required for the main frames consisting of columns and beams to stay within elastic region under strong ground motions. The energy dissipation provided by hysteretic dampers reduces the required strength. On the other hand, the total input energy is affected by plastic deformation, since the increase of plastic deformation means elongation of the apparent natural period and the total input energy depends on the apparent natural period. The benefit of hysteretic damping and the effect of plastic deformation on the input energy are evaluated individually based on the energy balance concept. An analytical expression of the required strength is formulated considering these two effects.
