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Bethlehem's crew
first erected the lower halves of the ribs and the connecting
purlins.
Next step was to
erect the upper halves of the ribs (welded splices), and install
purlins. Meanwhile, the tension ring was positioned on falsework.
When all cables were tensioned, the basic structure was complete.
This sectional
view greatly simplified, gives some idea of the interior. It
does not show a free-standing steel-framed stairwell at the approximate
center of the structure. Visitors enter, ascend ramps through
exhibits to an escalator, rise to the next level, and walk through
additional display areas spiraling around the building, then
descend to the exit. Administration and VIP offices are in the
main building, with mechanical equipment in a 100-ft. long one-story
wing.
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Here is a case where ingenuity
in engineering design was required to produce, economically,
a structure whose unusual shape was determined by promotional
considerations.
The Travelers' symbol is an umbrella,
so it was essential to base design of their exhibit building
on this shape. The final result was an abstract adaptation of
the umbrella, mirrored by a similar form below, resulting in
a scalloped-edge saucer which appears to be floating above a
continuous wall of water jetted up from a circumferential pool.
Actually, the main structure
is an oblate spheroid in elevation, with light outriggers added
to establish the umbrella "points." It springs from
abutments appended to a 23-ft.-high, scalloped-edged (in plan)
masonry wall which encloses the ground floor of the exhibit building.
Twenty-four weld-plate ribs, shaped like boomerangs, curve up
and out, then inward, leaving a 66-ft. diameter opening at the
apex. Diameter of the spheroid at its equator is 132 ft. Total
height above grade is 63 feet.
Closure at the pole is accomplished
with a remarkable space structure which, essentially, is a tension
"hub" of steel plates, to which the outward thrust
of the ribs is transmitted by steel cables.
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