The George R. Moscone Convention Center in San Francisco was opened to the public December 2, 1981. Built at a cost of $126 million, the center occupies an entire city block. It covers an area of 485,000 square feet, including a grand exhibition hall with a column-free area of 250,000 square feet and 31 meeting rooms capable of handling from 50 to 600 people. Concrete was the only material considered for construction of this predominantly underground facility.
The exhibition hall roof required a high rise to accommodate displays and equipment in a column-free hall, and it also had to be designed for heavy future loads, such as 3 feet of earth or 3 stories of light frame buildings. All of this was further complicated by the fact that the exhibit hall would be 10 feet below the natural ground water table. One of the largest foundation mats in the history of modern building construction, over 12,000 cubic yards of cast-in-place concrete reinforced by 8,000 tons of steel, was laid to counteract the resultant water pressure by its sheer weight. This mat ranges from 6 to 13 feet deep and covers and area 550 by 850 feet.
Post-tensioned arches were chosen as the primary structural support for the grand exhibit hall roof, as the best means of creating a light and airy open space underground. The 295-foot-span arches are designed to resist earthquakes and support future park landscaping and a 3-story building at street level yet they require only a 6-foot depth of roof structure at the center of the span. Because the Center will hold as many as 27,000 people at one time, special attention had to be given to fire safety and seismic resistance. Stairs and exit ramps leading from the exhibit hall and meeting room levels are encased in fireproof concrete exit tubes that are actually box beams which carry portions of the roof and floor loads. The design also assures survival in an earthquake 25 percent more severe than the famed 1906 San Francisco tremor.