Seismic Design Codes for Buildings in Japan

Two revised seismic design codes in the Building Standard Law of Japan, which were revised in 1981 and 2000, are simply reviewed with the transition of Japanese seismic design code in this paper. The central feature of the seismic code revised in 1981 was the introduction of a two-phase earthquake design. Allowable stress design was employed for first-phase earthquake design targeting the safety and serviceability of buildings during medium-level earthquake activity. Second-phase earthquake design, which is ultimate strength design, was added to provide safety against severe earthquake motion. On the other hand, the seismic code revised in 2000 precisely defines performance requirements and verification based on accurate earthquake response and limit states of a building. The capacity spectrummethod is used for evaluating the earthquake response. The code is applicable to any type of material and buildings such as seismic isolation systems as long as material properties are well defined and structural behavior is appropriately estimated.