November_1967 — Page 15

JAPAN

T

HE first large-scale development in Japan to take advantage of the Government's new building code abolishing height restriction is due for completion next year. With 36 storeys above ground and three below. the 147 metre high Kasumigaseki Mitsui Building in Tokyo is the city's first skyscraper.

Foundation work on the building started in July 1965 and the steel framework was completed in April 1967.

Finishing work for the total

TOKYO SKYSCRAPER Kasumigaseki Mitsui Building

by Shigenosuke Ishida,

Architect, Mitsui Real Estate Co., Ltd.

floor area of 155,846 sq. m. (1,677,- 506 sq. ft.) is due for completion by July 1968.

Before starting plans for the four acre site at Kasumigaseki 1 made two journeys to various cities in Europe and America to Inspect urban rede-

Kasumigaseki Mitsui Building viewed from the south

Far East Architect & Builder November, 1967

velopment schemes and to study the technology of tall building construc- tion.

I returned to Japan with a deep impression that in every city keen attention is being paid to the vital problem renewing decrepit urban areas and unfunctional city facilities. And as a result of my studies I con- cluded that an effort should be made with the Kasumigaseki project to im- prove the environment of this part of Tokyo.

Coincidently, at that time a new building code dealing with the volume of new structures was enforced to stimulate my ideas.

Building Code Revision

Under the old building code in Japan the height of buildings in city areas was not allowed to exceed 31 metres. The new building code, en- forced in July 1963, abolished height restrictions so long as the building was within the volume limitation stipulated in Tokyo.

When heights were limited to 31 metres it was usual, for economic reasons, to cover the whole site area with building. The result has been overcrowded developments cut by dark ravines and the creation of slum

areas.

Application of the volume stipula- tions to the site, while at the same time allowing as much ground and air space as possible, resulted in 36 typical floor areas of 38,111 sq. ft. (Fig. 1 and 2), and for the first time a building of 147 metres height was proposed in an earthquake zone.

Structural Design

According to the studies on aseis- mic structures made by G. W. Housner 1, and Dr. K. Moto*2, the greater the natural vibration period of a high-rise building, the less the effect of the seismic shock on the building, provided that it has a foundation based on a hard soil layer. The na-

*1 Professor of California Institute of

Technology, U.S.A.

*2 Vice-President of Kajima Construction Co. Ltd., and Professor Emeritus of Tokyo University.

41

Page 15Page 16

42

BALCONY