This complex of exhibition halls for the 1972 International Trade Fair was planned, designed and constructed in 22 months. Its large-span cast-in-situ concrete space frames were the first of their kind to be built in the world.
The choice of shape and form of the structural system was driven by its potential versatility: it contains an enclosure with a column-free main hall of 6700 sq.m, and four smaller halls adding an additional 7500 sq.m, under its roof structure. After investigating multiple alternatives, such as folded plates and hyperbolic paraboloids, a space frame system with a truncated pyramid as the basic module and overall form was adopted. Steel or pre-cast concrete would have been obvious choices of material for such a space frame, but the constraints of the available construction technology of that time necessitated the use of in-situ concrete.
After rigorous investigations into pyramid geometry, the rhombic section developed for all the members of this very large building may well be the secret of its ultimate delicate and light appearance. With chamfered faces of just 25cm in the Hall of Nations and 23cm in the Halls of Industries, and interface angles drawn from the slopes of its members, the robust rhombus allowed for the in-situ construction of the space frame where as many as nine to twelve members come together at one node. The innovative resolution of the nodes in this way provided the requisite strength at the node to absorb the heavy compressive or tensile forces from the members.
The large truncated pyramids of both structures are composites of smaller unit pyramids. The Hall of Nations consists of units of a 4.9m x 4.9m base and 3.5m height which form the 73m x 73m pyramid, truncated at the height of 30m with a roof span of 39m x 39m. The Halls of Industries are four 18m-high pyramids of 40m x 40m base, with truncated roofs of 22m x 22m, made of units that are 2.6m high and 3.6m x 3.6m at the base. The configuration of both these basic pyramids is such that all members of the square base and the four triangular sides have the same length, finally allowing the same building slope and the angle of this basic unit at 54°44’8”.