For decades, Japanese cities had a height limit of 31 metres. When it was lifted, what made skyscrapers possible in an earthquake country was a reversal of thinking: let the building bend and let the shaking pass. From the Kasumigaseki Building to the towers of Nishi-Shinjuku and hotels that put their lobby in the sky, we read a history of height.
The age of 100 shaku, 31 metres
Look at photographs of Tokyo or Osaka in the Taisho era and you notice how evenly the buildings line up. The Urban Building Act of 1919 set the height limit at 100 shaku, about 31 m, and 65 shaku (about 20 m) in residential districts. Some research finds little firm basis for the figure.
The limit carried over into the postwar Building Standards Act. Change came with a 1963 amendment, which created “floor-area districts” that limit how much floor area may be built relative to the site; inside them, the 31 m limit no longer applied. It was a shift from controlling the city by height to controlling it by volume. Absolute height limits were abolished entirely in 1970.
Some sources give the Keio Plaza Hotel’s height as 179 m.
Not stiffer, but more flexible
Even with the height limit gone, building tall in an earthquake country was not easy. The prevailing idea had been the “rigid structure”: make the building itself strong and stiff and resist shaking by force. Reinforced concrete was thought the most earthquake-resistant material, and rigid structures were said to top out at around 15 storeys.
Against this, Kiyoshi Muto of the University of Tokyo proposed the “flexible structure”: make the building light with steel, and let it bend like a willow branch so that the shaking passes. A stiff building shakes quickly back and forth and takes the full force of an earthquake; a supple tall building sways slowly and widely and slips that force.
This idea took shape in the Kasumigaseki Building, completed in April 1968: 36 storeys, 147 m. Mitsui Fudosan calls it Japan’s first skyscraper. Its columns used large, thick H-sections and its beams 15.6 m honeycomb girders; of about 15,000 tonnes of steel, some 11,000 tonnes were extra-thick H-sections. More than 70 percent of the site was left as open space, and the building’s volume of about 500,000 m³ even gave Japan a unit of measure: “so many Kasumigaseki Buildings”.
Above 60 metres, the state checks
Under today’s Building Standards Act, a building more than 60 m tall needs the approval of the Minister of Land, Infrastructure, Transport and Tourism for its structural safety. Recorded earthquake motions are fed into a model of the building, and “time-history response analysis” traces its movement moment by moment to confirm safety, building by building.
A recent concern is “long-period ground motion”. In a large earthquake, slow swaying motions travel great distances, and skyscrapers and isolated buildings with long natural periods are prone to resonate with them. In 2016 the ministry set out countermeasures for skyscrapers in the Kanto, Shizuoka, Chukyo and Osaka areas, with a Nankai Trough megaquake in mind. Installing damping devices is cited as effective.
Sway in the sky, and hotels
The upper floors of a skyscraper sway not only in earthquakes but in wind. Everyday sway is no danger to life, but in a hotel room even slight movement spoils comfort. So damping devices are installed on the roof or upper floors: masses that move against the building’s sway to cancel it out.
A device developed by Obayashi combines a mass that swings passively with one driven actively by computer, reducing sway from strong winds and small and medium earthquakes to about a third. It was used at the Yokohama Bay Sheraton Hotel & Towers. The calm of a skyscraper hotel rests on a weight you never see.
Nishi-Shinjuku: towers on a waterworks
The skyscraper district of Nishi-Shinjuku was born on the site of the Yodobashi water purification plant. Opened in 1898, the plant moved in 1965, and a plan to turn its site into a new Shinjuku business centre had been decided in 1960.
The Keio Plaza Hotel, opened in June 1971, has 47 storeys and stands 178 m tall; it was then the tallest building in Japan and the country’s first skyscraper hotel. In 1991 came Kenzo Tange’s Tokyo Metropolitan Government Building, its No. 1 Building 48 storeys and 243 m tall. And in 1994, designed by the same Kenzo Tange Associates, the 52-storey, 235 m Shinjuku Park Tower was completed. Park Hyatt Tokyo occupies its 39th to 52nd floors.
- 1898Yodobashi water purification plant opens
- 1960New Shinjuku centre plan decided
- 1965The plant moves away
- 1971Keio Plaza Hotel opens; Japan’s first skyscraper hotelJune
- 1991Tokyo Metropolitan Government Building completed (Kenzo Tange)
- 1994Shinjuku Park Tower completed; Park Hyatt Tokyo opens
Putting the lobby in the sky
In skyscrapers with a hotel stacked above offices, a “sky lobby” on an upper floor is common. At Park Hyatt Tokyo, the hotel begins when the lift reaches the 41st floor. Aman Tokyo in Otemachi Tower has its lobby on the 33rd floor, and Andaz Tokyo in Toranomon Hills checks guests in at its lounge on the 51st.
The entrance on the ground is small; the real front door is in the sky. A skyscraper hotel builds its ritual of arrival into the lift ride.
Feel the height when you stay
When you stay in a skyscraper hotel, before looking down at the ground, look across at the tops of the towers at your own height. There is a skyline in the sky that could not exist in the age of 31 metres. On a windy night, you may sense the building answering faintly behind the curtains.
Where to see this technique
- Park Hyatt Tokyo (Nishi-Shinjuku, 1994, Kenzo Tange): floors 39 to 52 of Shinjuku Park Tower, with its lobby on the 41st
Sources
- Morohoshi and Kato, “The history of absolute height regulation”, Journal of the City Planning Institute of Japan 40(3), 2005
- House of Representatives, Act partially amending the Building Standards Act (Act No. 151 of 1963); Tokyo Metropolitan Government materials
- Mitsui Fudosan press release (Kasumigaseki Building); Nippon Steel quarterly; Diamond Online
- Aomori Prefecture, review standards for Article 20; Oita Prefecture structural calculation materials
- MLIT press release, 18 December 2015; Osaka Prefecture, long-period ground motion measures
- Obayashi Corporation, history of technology (damping devices)
- Shinjuku City (Yodobashi plant and new centre plan); MLIT Kanto Transport Bureau; Gendai Business (Keio Plaza Hotel)
- Tokyo Fire Department (Metropolitan Government Building); Tokyo Bureau of Environment (Shinjuku Park Tower); hotel reviews and press
