Outline of earthquake provisions in the recently revised Japanese building code

Abstract

The revised building code of Japan, to become effective in June, 1981, is reviewed. It features a two-phase design for earthquakes. The first phase design is for medium earthquake motions, and this is basically the unchanged traditional seismic design. The new second phase design is intended to give protection to buildings in case of severe ground shaking. It requires the checking of several aspects of the building that has been proportioned by the first phase design. These include storey drift, vertical stiffness distribution, horizontal accentricity and ultimate lateral load carrying capacity. Both phases of the design are reviewed in detail, with some numerical examples where it is appropriate to illustrate the design procedure. Some provisions are discussed in the light of recent earthquake damage in Japan. A comparison with New Zealand seismic design loadings is also made.