Unisphere -- the
largest stainless steel structure in the world -- had quite a
heritage to live up to.
Modern World's Fairs usually revolve around
a symbol that captures the awe and imagination of all who see
it. The Paris Exposition of 1889 had the Eiffel Tower; the 1939
New York World's Fair -- its Trylon and Perisphere; and the 1962
Seattle World's Fair -- its Space Needle.
To this spectacular line-up -- add the
Unisphere -- one of the most inspiring and by far the
most difficult and intricate of Fair symbols to design and construct.
Fair authorities wanted a model of the
earth; an open sphere esthetically pleasing inside and out; from
any angle and under any lighting. It had to convey the impression
of lightness, grace, simplicity -- and yet had to be engineeringly
sound to face possible wind forces up to 100-m.p.h.
The structure also had to resist corrosion
since it will remain as a permanent feature of the park.
Problems? It was like balancing a beach
ball on a golf tee!
Some 1,500 unknown factors had to be resolved
to determine unit stresses. Complex modern buildings sometimes
force planners to solve thirty to forty simultaneous equations.
The Unisphere had six hundred and seventy just for one
of three sets of calculations into which the problems were divided.
The equations, which would take men years to solve manually,
were fed into advanced electronic computers. With the aid of
the computers -- which performed the necessary calculations in
minutes -- the answer was obtained in a matter of weeks. Only
steel -- stainless steel -- could do the job.
The engineering talent and experience of
U. S. Steel's American Bridge Division -- the people who built
such structures as the Empire State Building, the U. N. Headquarters,
and most of the world's great bridges -- were put to the test.
Supports could not be placed according
to expediency. They had to follow the parallels and meridians
of latitude and longitude to retain the desired visual impression.
Where no known fabrication technique sufficed,
engineers would invent one!
Land masses were built up in layer-cake
style -- like huge contour maps conforming with the topography
of each continent. The finishing touch was the addition of 3-ton
orbital rings, representing the paths of man-made satellites
now circling the earth.
The entire stainless steel structure rests
on a 70-ton open sculpture of high-strength U. S. S. Cor-Ten
steel, anchored by U. S. S. "T-1" constructional alloy
The Unisphere, made practical by
modern computers, was made possible by modern steels and the
ingenuity of American industry. Fair President Robert Moses --
at the start of construction of the Unisphere March 6th,
1963 -- said: "What stronger, more durable and more appropriate
metal could be thought of than stainless steel?"
The gleaming symbol -- unforgettable in
its majesty -- stands among other great industrial attractions
that echo the invitation, "Come to the Fair," to see
and thrill to the imagination of America's builders.
Source: United States
Steel Press Release, March, 1965