Sapporo Dome
Sapporo, Hokkaido Prefecture, Japan
Hiroshi Hara

With its moving grass playing field, this stadium is a feat of engineering

© Tomio Ohashi

For more photos click on 'photos & drawings' above. To see the people and products behind this project click on 'people & products.'

By Naomi R. Pollock, AIA

In 1996, Sapporo conducted an international competition for the design of an all-weather dome on the outskirts of the city. The new building had to include a professional-grade baseball diamond and be able to host events such as rock concerts and large exhibitions, as well as World Cup soccer, since Sapporo would serve as a host city. The greatest design challenge was the local climate. During the winter, Sapporo’s daytime temperatures are well below freezing, and winds from Siberia buffet the city all season long. But precipitation is the real problem: Each year the city gets a whopping 20 feet of snow. Predicting how the snow would behave on a long-span roof was extremely difficult.

Because of the harsh weather, the grass playing field had to be covered. At the same time, the field required four hours of direct sunlight every day for the grass to stay healthy. To resolve this conflict, the architect had to find a way to move either the roof or the field. Because of the snow load and other climactic conditions, the use of a retractable roof was eliminated from the start. The only option was to move the field.

Shaped in plan like a figure eight, the architect’s proposal consisted of two arenas, one indoors and one outdoors, with a soccer field that glides back and forth between them. At grade, the stainless-steel clad, 43,000-seat indoor dome looms over its wide-open site like a gleaming flying saucer.

The dome’s aerodynamic form grew out of the need for a roof that could not only withstand and deflect the snow but also shelter a vast, column-free space. Spanning 804 by 745 feet, the roof is supported by a shell structure composed of 13-foot-deep space trusses that transfer their loads to a ring of columns at the building perimeter. The dome’s flat end opens onto the outdoor stadium. Here an internal "bridge" and tension cables complete the structural loop by channeling loads to either side. While sheets of glass seal the bridge’s double-deck slot of space, a 50-foot-tall moving wall underneath opens up like traditional Japanese sliding doors to let the soccer field pass through at ground level.

While rolling out synthetic turf and adding a fake pitcher’s mound are all it takes to turn the arena into a baseball field, the conversion to soccer mode requires moving an 8,300-ton field. Composed of structural steel, concrete, sand, and grass, the "hovering stage" literally glides from outdoors to indoors like a magic carpet. First, air is blown in and trapped with perimeter seals under the field, which reduces the field’s weight by one-tenth. Then the air’s pneumatic force of 1.09 atmospheres propels the field forward at a rate of 4 meters per minute while wheels and floor-mounted sensors guide its course.

Once the field enters the building, it rotates 90 degrees on a pivot to face the main grandstand. The five-hour conversion is complete after four groups of movable seats are locked into position.

See the May 2002 issue of Architectural Record for full coverage of this project.

Formal name of Project:
Sapporo Dome www.sapporo-dome.co.jp

Location:
Sapporo, Hokkaido Prefecture, Japan

Gross square footage:
98,281 sq ft

Owner:
City of Sapporo

Architect:
Hiroshi Hara
10-3 hachiyama-cho
Sibuya-ku, Tokyo JAPAN
tel:81-3-3464-8670
fax:81-3-3464-8612