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The Ōita Bank Dome was designed by Kisho Kurokawa and built by KT Group for the World Cup Games in 2002. Its nickname, The “Big Eye” Stadium comes from the fact that the roof resembles (when opening and closing) the winking of a human eye.
The most amazing feature of The “Big Eye” Stadium, the one that makes it one-of-a-kind is the retractable roof. A dome is a construction method meant to shelter a structure, its roof. The romans were the first pioneers for this type of covering and have built the largest concrete (not reinforced however) dome. Architects and engineers have built of course bigger and bigger domes, always exceeding the boundaries set by previous builders. The “Big Eye” Stadium however is the biggest yet, a truly incredible piece of engineering that took dome building to a whole new level. This memorable structure wouldn’t have been built without some amazing technology features which made possible not just the covering of stadium but also its ability to retract. The roof is in fact made of two giant parts that close right above the spine set on the N-S axis of the stadium. The weight of the entire structure is supported by perpendicular horizontal-running sub-beams, symmetrical to the axis of the spine and intersecting in its vertical plane. The two giant parts of that form the eyelashes of The “Big Eye” Stadium are supported by these ribs and can move along their length to open or close the roof. To move so much weight and with incredible precision, the engineers have created a system featuring thick steel wires on each rib that are tied to the roof and a winch member (one for each rib) set at the bottom. This enables the roof to open or close at the touch of a button. The complexity of the system stands in the fact that each rib has a different curve ratio from the others, and each wire, a different load. This means that in order to open The “Big Eye” Stadium, each wire must be pulled by its winch with a unique load that is calculated and recalculated constantly so that every winch would pull in a unison with the others; all of this is possible because of state of the art technology and programing that controls the loads and sets a different pulling power for each winch.
“It might be just coincidence but we have a pineal gland in the brain that is said to be a degenerated eye-like organ. It seems that we had a third eye in our brain to look up the sky, rather than two eyes to see the world on the earth. Since people abandoned the universe to stay on the earth, the third eye became useless and degenerated. Seeing the Big Eye watching only the sky, such a thought came to my mind.”
In order to get the maximum amount of sunlight, the designers have placed The “Big Eye” Stadium on the north-south axis which coincides with the main beam arch so that when opened, there will be almost no shade casted onto the field by the structure itself. The stadium was designed to be as comfortable as possible, always having in mind the spectators and the players. Between the giant roof and the spectator seating is a slit which enables ventilation and quite a view of the mountains. At the same time the spectators will not feel enclosed in a giant steel structure but somehow always connected to the exterior world by the wind and sun that penetrate the stadium through that slit. One of the biggest problems a dome may face is fire which, if the structure is closed it will emanate smoke which will have no place to go out through, threatening the safety of the spectators. The “Big Eye” Stadium however doesn’t have such an issue and moreover, it has some pretty amazing fire safety features that make the visitors all the more comfortable. The designers have incorporated a system composed of cameras, sensors and giant water cannons that can detect a fire instantly and deploy water to its location, drastically reducing the chance of a fire spreading. To enhance even further the sensation given by the stadium to the spectators, seats were placed right up to the edge of the field. Normally this wouldn’t be allowed because it is very inconvenient for track events but the engineers have solved the problem through a retractable seating system.
The “Big Eye” Stadium is not just a stadium but an all-purpose sports park, the stadium being just a part of it. The ensemble will host several facilities that include a general fitness center, a training and lodging center, a botanical pool, 2 multi-purpose athletic fields, 2 soccer and rugby training fields, a sub-training field, a softball field, a public baseball field, 11 tennis courts, a throwing event practice field, a gate-ball field and large open field that can be used year-round because of the retractable roof feature.
This is the result of engineering ingenuity. Some might think that this is a an architectural project but I believe it’s all about engineering, overcoming great structural difficulties from which a beautiful shape emerges. I say this because I’m pretty sure that the designers chose the spherical shape not because it looked beautiful and made a human eye effect possible, but because it was the only one suitable for the task. This means that The “Big Eye” Stadium’s form was not designed to be intriguing but to be a unique structure, whose only purpose is functional and its design is the consequence of the process of overcoming problems given by gravity and the limits of the materials used in the construction process. The beauty of the stadium comes from the never ending man’s desire to conquer nature and cancel, oppose to its laws (gravity, pressure, temperature etc.)
Photo courtesy to Taishi, Wikipedia Commons
Project Name: Ōita Stadium (Big Eye)
Broke ground :1998
Owner: Ōita Prefecture
Operator: Daisen Co., Ltd.
Construction cost:208 mln $
General contractor: Takenaka Corporation
Field dimensions:105 x 68 m
Building Area: 51,830 m²
Total Floor Area: 92,882 m²
Covered Area: 29,000 m²
Stand Inclination: Max. 33 degree angle