feet (78 meters) above the playing field, consists of two movable panels that retract across the short span. The designer was Rob Schuurman. Bank One Ballpark in Phoenix, Arizona, designed by Ellerbe Becket, was completed in early 1998. Two 200-horsepower motors open or close the retractable roof over the 48,000-seat stadium in under five minutes. Each half of the roof consists of three movable trusses that telescope over a fixed end truss. Either side can be opened to any position, independently of the other. The 52,000-seat Colonial Stadium in Melbourne, Australia, was opened in 2000. Its 540-foot-span (165-meter) retractable roof, employing a lightweight space-truss structure, opens or closes in less than eight minutes. Other arenas, such as the Sports Park Main Stadium of the Oita Prefecture, Japan, and Miller Park, Milwaukee, Wisconsin, were completed in 2001. The former, designed by Kurokawa Kisho Architectural Urban Design and the Takenaka Corporation, has a retractable 895-foot-diameter (274-meter) hemispherical steel-framed shell roof; Miller Park has a seven-panel roof.

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Amsterdam Arena, the Netherlands; Rob Schuurman, architect, completed 1996. Aerial view, with the roof closed.

See also

Colosseum (Flavian Amphitheater)

Further reading

Crawford, Bob. 1998. Diamond in the Desert: A Pictorial Visit to Bank One Ballpark. San Francisco: Woodford.

O’Malley, Martin, and Sean O’Malley. 1994. Game Day: The Blue Jays at. SkyDome. Toronto and New York: Viking.

Petersen, David C. 1996. Sports, Convention, and Entertainment Facilities. Washington, DC: Urban Land Institute.

Roman concrete construction

Concrete is made by mixing broken stone or gravel and sand (aggregate), a bonding agent, and water, and allowing the mixture to harden through chemical process into a solid mass. So-called cementitious materials had been used in ancient Egypt about 3,000