Abstract
In this paper, it is expressed how the period elongation and damping due to the plasticity of a building influence on the required horizontal force of a building. In order to obtain the result, based on the formula of the required lateral force using the equivalent linearization technique proposed previously by authors, the bi-linear restoring force model was used. Moreover, the significance and problems of the method for lateral load carrying capacity of the current seismic regulation are discussed, based on the knowledge acquired from these investigations. Furthermore, the correction method for lateral load carrying capacity is proposed for more rational regulation.