TAJIMA SPIRALDOME

A・D・H Architects

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A Fiction Named Competition

English Text by Yoko Kinoshita

As we worked on the Tajima Dome Competition we had been reminded of architects as creators of fiction. The reason being multifold.

This competition was a two-stage competition in which our scheme was selected as one of the five finalists in its first stage. The second stage was to be submitted by general contractors that petition to pair up with a finalist of their choice. The two-stage competition as such where the second-stage entry is prepared in collaboration with a general contractor is recently becoming popular in our country. But the unique aspect of this competition was that it attempted to distinctly differentiate the design aspect (first stage) from that of its practical implementation (second stage). In other words the first stage was opened to all designers, and was evaluated purely on design concepts. The second stage on the other hand, was left to general contractors to make technical suggestions for realizing the design scheme of their choice. Moreover, this competition allowed for multiple entries in the second stage, a competition procedure which was unprecedented.

There is basic difference in criteria between design competitions and competitions such as the Tajima Dome which now known in Japan as "business competitions" when literally translated into English. The former is evaluated solely on the quality of design while the latter is judged not only on design, but also on its practicality and building cost. Since the maximum cost is usually stated in the program, this type of competition puts a burden on general contractors to take responsibility and risk involved in implementing the design.

After our scheme was chosen in the first stage, we were pleased to hear that two contactors, Takenaka and Tokyu had petitioned to develop our idea. (There was another finalist with multiple contractors petitioning for the second stage, but at the end we were the only one with multiple second-stage entries.) We were honored to have two contractors petition for our scheme as if that was an assurance for the validity of our idea. But little did we know of the implications embedded in this new system of competition.

It did not take long for us to realize the discrepancy. During the second stage we made a particular effort to be fair to both our contractors and take a neutral stance in dealing with them. We saw our concept take off in two different directions, but we could not take active role in reconciling the two to create one complete scheme as otherwise done in our ordinary design development circumstances. We further realized that in the event one of our schemes becomes a winning entry, it means that our other scheme automatically becomes a loser. To these dichotomies, we as designers felt the frustration. The competition, needless to say, ended in fiction.

The site of the Tajima Dome lies in the beautiful foothills surrounding the Mount Kan-nabe in Hyogo prefecture. The program called for a multi-purpose dome that accommodates both sport activities as well as various events.

Factors considered were: how to span 150 meters in diameter, what to do about heavy snowfalls in the winter, how to exhaust heat in the summer, and ventilation. We had to also meet the requirements for acoustic environment and lighting conditions for both sports and events that called for different environments.

The notable characteristic of our idea which we called the Spiral Dome is a roof that is composed of the double spiral. Spiral form of the sloping roof is useful for rain drainage as well as clearing snow. The stepping ceiling is beneficial for acoustics and the clearstories created by the tiers could be opened up for ventilation as necessary. And lastly, the long slope generated by the spiral becomes a path for people to climb for leisure. A man-made hill of 45 meters in height which at times become a panoramic viewing deck, while at other times act as jogging course was in our view an inspiring solution for sports dome.