Simplified sketch of the basic structural scheme -- eight giant trusses.

Outer truss

Inner truss

Functionally it's a building, but structurally it's a bridge. Or, more accurately, four bridges.

The sketch [left] illustrates the basic structural scheme. Essentially, it consists of four 310-ft-long inner trusses, spanning some 174 c-c of the supports, and extending out 68 ft to support the outer trusses. Both inner and outer trusses are 57 ft high, c-c of top and bottom chords.

Design of the outer trusses is evident in the photograph [above]. The top and bottom chords, and the major vertical and diagonal members are 14 WF sections of various weights, while secondary horizontals, verticals, and diagonals are back-to-back angles up to 8 x 4 x 5/8 in size.

The most unusual truss members are the hangers of the inner trusses (the massive diagonal shown [above]), which are 81 ft long and are designed for a load of 3595 kips. They are made up of two 32-in.-wide by 2 1/2-in.-thick plates of A441 steel, with added reinforcement at each end, tieing into massive (roughly 8-ft-sq x 2 1/4-in.-thick) A441 gusset plates top and bottom.

The United States Pavilion occupies a 4 1/2-acre site. It rises above a landscaped plaza, or podium, about 6 ft above grade. Visitors proceed under the structure, and up escalators to a court atop a truncated pyramid, from which point they cross to the lower level of the building by means of 39-ft-long steel bridges. Exhibits illustrating the theme, "Challenge to Greatness," are located on the first floor, along with an auditorium, VIP reception rooms, and staff offices, all of which occupy one entire segment of the first floor. A ride transports visitors through the second floor exhibition area.

View from inner court during steel erection..

THE SUPPORTING TOWERS

The structure's four supports, too, are of major interest. Each is a tower, comprising four individual box columns on 11-ft centers, tied together with heavy bracing. Three of these cores form stairwells, while the fourth contains an elevator shaft. The columns are of welded plate construction, about 26-in. square, using plates as thick as 2 3/8-in., and with additional reinforcing plates.

Steel supports saved 20 per cent of the total weight. Originally, the structural design specified that the column bearings would be located just below the first floor level, where they would stand on reinforced concrete piers some 25 ft high, and nearly 25 ft sq in plan. However, the poor substructure conditions made it necessary to lighten the total structure as much as possible. Re-examination disclosed that by simply extending the steel columns another twelve feet down, thus eliminating about one-half of the reinforced concrete, the total dead load was reduced by some 20 per cent!

To provide for leveling the gigantic structure, each tower is equipped to receive eighteen 300-ton-capacity hydraulic jacks.

Also, an 11-ft-wide moving ramp, carried on steel beams, extends from a point on the second level some 80 ft across the diameter of the center well to an opposite point on the third level. It carries the visitors leaving the theaters to additional exhibits above, after which they descend the spiral ramp.

At the third level, radial 27 WF 94 girders connect to the circumferential box girder and extend inward to support the top exhibit area. Inboard, these girders tie into a hexagon of 36 WF 300 girders, supported by six main columns. The radial lines are continued with 18 WF beams, from each of which are hung the 6 WF 15.5 hangers that extend to the second-level framing.

The United States Pavilion is operated by the United States Commission, Department of Commerce, Norman K. Winston, Commissioner; Construction Supervision: General Services Administration; Architect: Charles Luckman Associates of New York and Los Angeles; Exhibit Design: Usher-Follis, Inc.; Cinerama Camera Corporation; Structural Engineer: Severud-Elstad-Krueger Associates; Mechanical and Electrical Engineer: Slocum & Fuller; General Contractor: Del E. Webb Corp.; Steelwork: Bethlehem Steel Company.

THE FLOOR FRAMING

The framing spanning 66 ft between the inner and outer trusses is also of extremely heavy construction, especially at the deeply cantilevered corners. Wide-flange floor beams vary from 16 through 36 in., both at this level and at the second floor, while roof beams range from 14 in. through 36 in. Both floors and the roof are concrete slabs over 3-in.-deep formed galvanized steel decking. Floor-to-ceiling height of the lower level is 18 ft; second level is 23 ft.