A Colossal Floating Wing



A Colossal "Floating Wing" 
Artist Rendering - B&W

 Full Steel Frame - front

Truss Vertical

A typical truss vertical shown at Bethlehem's Pottsdown Fabricating Works illustrates some of the complexities of the structure. All of the vertices were built up of steel plate, with precisely skewed web plates. Note the extreme thickness of these plates.


Early stage of steel erection

An early stage of steel erection. Virtually all field connections were welded and radiographed.


Cutaway sketch

Cutaway sketch of the structure at its midpoint shows how the ride passes through the "long" U-frames; mechanical equipment is housed in the "short" U-frames.

This structure would be notable if it were just a fraction of its actual size; in fact, it is 400 ft long, and 200 ft wide at its longitudinal midpoint, where it is about 60 ft deep. It spans 180 ft between supports, and cantilevers 108 ft beyond them. Also, along the entire 400-ft length of the structure, it cantilevers from the trusses as much as 66 ft toward the front, and 38 ft toward the rear.

This vast volume is supported on just four steel piers, two of which are designed for a load of 4,200 kips each, and the other two for a load of 2,500 kips each!

These supports, each 35 ft high from bottom of base plate at grade to center of bearings, rise through a base structure structure which occupies virtually the full 105,000-sq-ft site. This structure, which contains exhibits, offices, VIP reception rooms, etc., is not described here. We shall confine our description to the "wing", which houses a chair ride which transports visitors through a series of theaters.


Basically, the wing's framing relies on a dual backbone of two trusses which extend the entire length supported by the four pylons, and forming a pointed ellipse. The trusses very in depth from 15 ft 7 in. at each end to 42 ft at the midpoint. Members were fabricated by shop welding, erected piece-by-piece, and field-welded. Although the trusses curve in plan, each of the eleven 36-ft panels is straight; all curvature is provided by skewing the flanges and connection plates of the verticals.

 Steel Framework - side view

The transverse frames at the extreme ends were erected after all U-frames were in place. The completed structure gives no outward hint of the pointed effect so evident in this picture.

Transverse ridge bents connect the two trusses, spanning 38 ft c-c of truss verticals near the ends of the wing, up to 94 1/2 feet at the longitudinal midpoint. The three end bents are of welded-plate design; the rest are trussed.

To achieve the cantilevers along the front and rear of the wing, U-frames are connected to the truss verticals at each panel point. These frames are shop-welded, using reinforced 36-in. wide-flange shapes. All but those at the ends (and the bottom members at the pylons) are pin-connected to the truss verticals.

Tension ties extending from the "front" truss U-frame connection points diagonally down to the lower members of the transverse bents, help take the "kick" from the U-frames. They are made up of two 18-in., 58-lb channels, back-to-back, with spacer plates.

Lateral Secondary Framing. It should be noted that there are no floors, per se, in the wing. Its huge volume is occupied by the ride and its framing members, a series of theaters, a projection booth, the mechanical equipment, and necessary catwalks and platforms for access. There is, therefore, no conventional floor framing, nor the added rigidity ordinarily furnished by a floor system.

The primary lateral members between transverse frames are beams of various sizes, welded in place. Generally speaking, the exterior shape of the wing is established by L series open-web joists, equipped with outriggers, which establish the architectural overhang at each bent line.

A major problem in fabrication and erection was the requirement that all external steel members adhere to a trace line with an accuracy of +-1/16 in., to assure absolute smoothness of the skin.

Supporting Columns. Although given an architectural finish that disguises their structure, the wing's supports are structural steel. The trussed pylons, used at the front of the wing, 14 WF 228 legs. The one shown at the [right] measures 30 ft 8 1/2 in. from top of base plate to bottom of bearing shoe.

Diagonal member

The heavy diagonal members shown here help transmit the "kick" from the long U-frames.


Front, trussed pylon

One of the two front, trussed pylons. It is the only support equipped with rollers to permit slight movement, horizontally on the "wing's" longitudinal axis.



Architect: Harrison & Ambramovitz; Exhibit Design: Harrison & Ambramovitz; Consultant: Henry Dreyfuss; Producer-Designer, Ride: Joel Mielziner; Structural Engineer: Paul Weidlinger; Mechanical and Electrical Engineer: Syska & Hennessy, Inc.; General Contracter: George A. Fuller Company; Steelwork: Bethelehm Steel Company


Whereas all other bearings are fixed, this one has rollers which permit slight horizontal movement to compensate expansion and contraction due to temperature changes. All bearing shoes are massive, measuring 7 ft 6 in. by 7 ft 2 in. in plan.

The two rear pylons are free-standing clusters of four 14 WF 184 columns, groove-welded to plates top and bottom. They are not braced and permit slight bending.

Ride Framing. The chair ride, which will take 4,000 visitors an hour on a 1,000-ft-ride lasting twelve minutes, required a rather complex framing system. It not only follows an irregular path in plan, but it has two lanes, one higher than the other, as well as a number of changes of elevation.

The main carrying beams are 18 WF 96 sections, with 6 B 15.5 filler beams. Along the front of the wing, within the U-frames, the ride rests on 18 WF beams connected to the upper flanges of the lower members of the U-frames. Elsewhere, however, the entire ride is elevated on columns.

Bethlehem Steel Logo
Source: "World's Fair Preview" -- Bethlehem Steel Co. (Courtesy of Tom Wentland)
View of Bell System Pavilion from the Pool of Industry 

Photo Lab transparency

Source: Commercial Transparency by Photo Lab, Inc., Washington, DC(Courtesy of Bradd Schiffman)


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