Aerodynamics of the Perisphere and Trylon at World's Fair

There can be no better way of beginning this paper than to quote the following recommendation from the pamphlet, entitled “Standards of Design for Structural Steel,” (1) published by the United States Navy Department:

“For structures of unusual character or magnitude where the wind is an important factor, the actual distribution and intensity of positive and negative wind pressure should be investigated, preferably by wind tunnel tests of a scale model, and the stresses calculated on that basis should be used if they exceed those determined from the formula given herein.”

Certainly the Perisphere and the Trylon, the “theme” buildings at the New York World's Fair, come under the designation of structures of unus u al character and magnitude-since the Perisphere is a hollow spherical building with a diameter of 200 ft, and the Trylon is a tapered triangular prism-like object, 675 ft high. The group, with a variety of supports for the sphere collars and columns, is shown in Fig. 1. The difficulty in estimating the wind loads, and especially their distribution, on these two buildings was all the greater since they are in close proximity to one another; Because of mutual interference they must be considered as a single aerodynamic unit, since no prior experimentation was available as to the aerodynamic effects on a sphere close to the ground, and since, in general, the contemplated project is without parallel in structural history.