Abstract: Relations between the elastoplastic inter-story drift of frame and the deformation of members are studied. Introducing the plastic deformation distribution factor χ as a parameter, the relations among χ, displacement ductility ratio μ_δ and column overstrength factor η_c, namely χ-μ_δ-η_c equations, are presented. Furthermore, the rules of drift decomposition are developed. By decomposing the drift demand, the target deformability of beams and columns are determined, which is a key step of the displacement-based design.