U.S. Pavilion at Expo 70

Osaka, Japan

Architects: Davis - Brody; deHarak, Chermayeff & Geismar (designers)
Roof Structural Engineers: Geiger - Berger Associates

Listen to the Introduction

The U.S. Pavilion at Expo 70 in Osaka is one of the very few embodiments of major technical and architectural innovation that was also built quickly and inexpensively. Trying to best R. Buckminister Fuller's Geodesic Dome built for the U.S. Pavilion at Expo 67 in Montreal (figure 1), the architects of the Expo 70 Pavilion first envisioned it as a huge floating sphere, inspired by NASA's Apollo 11 mission that put the first man on the moon (figure 2). This spherical scheme was the winning entry (submitted by Davis - Brody Architects and deHarak, Chermayeff & Geismar, Designers) in a competition sponsored by its future owner, the United States Information Agency (USIA). The competition scheme would have included exhibition space inside the sphere, and used its inner surface as a giant projection screen for continuously played film clips. The Pavilion ultimately erected at Osaka marked the birth of a new structural building type -- the longspan, cable stiffened pneumatic dome -- which would for a time become the predominant roof system over America's emerging sports palaces (figure 3). Remarkably, the U.S. Pavilion's pneumatically supported 465 foot by 265 foot clear span dome was developed largely in response to Congress' 50% reduction in the project's budget. The completed Pavilion cost $450,000, which was about half the cost of the Montreal dome.

Despite its extraordinarily economical $4.5 per square foot cost, the U.S. Pavilion was a masterwork of structural elegance and recent technological advances. The interior of the Pavilion was inflated like a balloon, putting its entire roof in tension, and allowing it to be made of fabric and cables. The completed roof's 1.5 pound per square foot weight was only one fifth that of the Houston Astrodome's, built in 1965. The Pavilion's primary structure and enclosure systems were made from only four materials: vinyl-coated fiberglass fabric and steel cables for the roof, held in place by a reinforced concrete ring girder resting on an earth berm (figure 4). The roof's fiberglass was initially developed by NASA as an extremely fire-resistant material after the death of three astronauts on a launching pad in 1967. It would have been impossible for engineers to predict the roof's aerodynamic but flexible behavior in Osaka's typhoon winds without the help of recent advances in computers and numerical analysis techniques. The earth berm supporting the roof was built of soil excavated from the site to make room for the lower levels of the Pavilion, and was simply bulldozed back into place when the building was disassembled.

The elegant simplicity of the U.S. pavilion's architectural detailing both harmonized with and emphasized its new structural form. Exhibition platforms were laid out to follow the diamond pattern of the roof cables above. The fiberglass fabric roof was translucent, allowing diffused sunlight to provide most interior lighting during the day; at night interior electric lights made the roof glow softly when viewed from outside. Interior finishes and exhibitions celebrated advanced and emerging technologies. The earth berm was covered with then-exotic foil-faced Mylar; the USIA used artifacts like the Apollo 11 space capsule to extol NASA's achievements. These features expressed a utopian view of technology that the Pavilion's architects and engineer embraced when describing future applications of pneumatically supported domes. Soon after the completion of the U.S. Pavilion, engineer David Geiger claimed that "there appears to be no maximum span for application of this type of roof," and architects Davis-Brody published plans for enclosing an entire town underneath similar structures.


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