Oita Winks for Soccer
From above, the Big Eye looks like just that; imagine what the birds must think when they fly overhead! The structure is an eye not only by its unique appearance, but also by its function. Its retractable roof can "blink" to adapt to conditions of use and weather. Also, the Teflon membrane panels, with 25 percent light permeability, removes the need for electric lighting during the day.
After three years of construction, the Big Eye finally opened its gigantic eye in March 2000 and is now taking aim on the big game: the 2002 International Federation of Football Associations (FIFA) World Cup.
The games will be broadcast with help from another eye. A high-tech moving camera installed on the main beam 200 feet (60 meters) above the field will deliver dynamic images to the rest of the world to keep their eyes wide open as well.
To give the field adequate sunlight exposure, the elliptical roof opening runs along the north-south axis. The structure of the main arch with perpendicular, horizontal-running girders corresponds to the elliptical shape of the roof opening. The pipe-arch structure, a large space frame, is perhaps the most economical design for the wide span.
The materials used for the main structure are steel frame and reinforced concrete; the upper skeleton consists of arch frames and triangular lattices. The lower skeleton is a rigid frame with seismically resistant walls.
A slit between the roof and the spectator seating permits both natural ventilation and a wonderful view of the mountains beyond. Seated spectators immediately notice that the slit not only creates a comfortable atmosphere, but eases any sense of claustrophobia.
The Retractable Roof
The stationary portion of the roof is clad in titanium, giving it a futuristic appearance. The noticeable interior lightness is thanks to the Teflon panels of the movable roof structure. This membrane is not only lighter in weight than glass, but it has great tensile strength and is durable and impermeable to any weather.
The retractable roof operates with a drive-type wire traction system. When closing, the roofs move up from two sides along the main beam arch, meet exactly above the center of the field, and close.
During this operation, computer systems monitor the precise tension of the wires and control their operation at highest efficiency. There were no precedents of such a large retractable roof structure, but it is evident that its simple form does a lot to optimize its operation and lower the cost.
Flexibility Accommodates Sport and Site
Depending on the particular use, 9,000 seats out of the total 43,000 can be retracted automatically. The whole stadium is so changeable for various functions that it again reminds one of a living being.
For example, to enhance the spectators' feeling of being part of the soccer game, the spectator seating can be literally moved forward to the edge of the soccer field. During track meets, the seating moves back to accommodate the slightly longer track field.
Through the gentle curves of its spherical design, the stadium merges with its surroundings. The sphere is an expression of an abstract symbol, but the shape also enables the retractable portion to move along its surface smoothly.
Kurokawa comments: "In the concept, there was a giant sphere buried in the ground, and what we see as a stadium is only its edge." This reminds us of Renzo Piano's Kansai International Airport, 1994. Piano used a similar geometry in its design, but it spreads horizontally because he imagined a circle instead of a sphere.
The Oita Stadium has already been chosen as a venue for the 2002 FIFA World Cup. But in anticipation of the 2008 Second Tour of the Japanese Inter-Prefectural Athletic Competition, it will continue to grow, eventually to become a large-scale and extensive all-purpose sports park on the 618-acre (250-hectare) site.
Shigekazu Ohno is an architectural journalist based in Tokyo. He writes for Casa BRUTUS and other publications.