earliest practical applications of concrete shells in architecture took place in Germany
during the early 1920s. The basic mathematical formulas for shell designs were
developed by Franz Dischinger and Ulrich Finsterwalder, employees of the Dyckerhoff-
Widmann engineering firm. Dischinger, along with Walther Bauersfeld of the Carl Zeiss
Encyclopedia of 20th-century architecture 560
Optical Company, designed the first major concrete-shell roof for the Jena Planetarium in
1924. To create the 82-foot hemispherical dome, a thin layer of concrete was sprayed
over a skeletal frame of reinforcement bars. This technique became known as the Zeiss-
Dywidag, or “Z-D,” process. By the 1930s employees at Dyckerhoff-Widmann, along
with engineers in Spain, France, and Italy, began designing other forms of concrete-shell
roofs,
Kresge Auditorium Massachusetts
Institute of Technology, shown from
the rear, roof being replaced, designed
by Eero Saarinen (1955)
including barrel vaults, octagonal domes, and hyperbolic paraboloids.
The introduction and early promotion of concrete shells in the United States stemmed
primarily from the efforts of one man: Anton Tedesko. By 1932 Tedesko, an employee of
Dyckerhoff-Widmann, had moved to the United States and persuaded the Chicago
engineering firm of Roberts and Schaefer to acquire the American rights to the Zeiss-
Dywidag process. The first building in the United States to take advantage of this
technique was the Brook Hill Farm Dairy Pavilion, built in 1934 for the Century of
Progress International Exposition in Chicago. The multi-barrel-vaulted building was
designed by Richard Phillipp. Roberts and Schaefer served as design consultants. Within
months the engineering firm was also involved in the design of a concrete-shell dome for
the Hayden Planetarium at the American Museum of Natural History in New York City.
Entries A–F 561
Articles on these buildings, appearing in both engineering and architectural journals,
promoted concrete shells as an ideal solution for roofing large, unobstructed spaces, as
they eliminated the need of rafters, purlins, or heavy trusses and were considered
fireproof. The development of reusable formwork in the construction of concrete barrel
vaults made shell roofs economically competitive with steel-truss designs.
Roberts and Schaefer dominated the American concrete-shell market prior to World
War II. By 1941 the firm had built concrete shells covering almost ten million square feet
of area. Most of their commissions during these years consisted of barrel-vaulted airplane
hangars and sports halls. Included was the Hershey Sports Arena in Hershey,
Pennsylvania, which, when completed in 1936, was roofed by the largest concrete shell in
the world. During World War II concrete shells provided an ideal alternative to steel
trusses for roofing large structures, including the many warehouses, factories, and
hangars built to meet war-related needs. Benefits of concrete shells recognized by the
military included speed of construction, ability to withstand intense heat, and, if the
structure became damaged, ability to change distribution of stress.
After the war other American architects and engineers became involved in the creation
of concrete shells. Most notable was the New York engineering firm of Ammann and
Whitney. The company developed its own barrel-vaulted shell design, which it then used
in the construction of a series of wide-span airplane hangars, including a double hangar
for American Airlines (1948) at Midway Airport in Chicago. In the mid-1950s the firm
worked with Eero Saarinen on several of the architect’s innovative shell designs,
including the curved, equilateral triangularshaped roof of Kresge Auditorium at the
Massachusetts Institute of Technology and the fluid, bird-shaped Trans World Airline
Terminal in New York.
The organic shape of Saarinen’s TWA Terminal reflected a desire among architects
around the world in the 1950s to take advantage of the ability of shell structures to be
molded into a wide range of artistic forms. The Spanish engineer Felix Candela explored
a variety of hyerbolic paraboloidal forms in his designs for thin-shell buildings in
Mexico, such as the dramatically cantilevered entrance canopy of the Ciba Plant (1955)
in Churubusco. In Italy, Pier Luigi Nervi explored the use of concrete ribs in aesthetically
pleasing designs to strengthen large concrete roofs, including the shallow dome of the
Palazzetto dello Sport (1957) in Rome. Le Corbusier’s hyperbolic paraboloidal shell
design for the Phillips Pavilion (1958) at the Brussels International Exposition was just
one of several exhibition halls at the event to include a concrete-shell roof. Roberts and
Schaefer also experimented with new shell forms in the late 1950s, as illustrated in their
involvement with I.M.Pei on the roof design for his May D and F Department Store
(1958) in Denver, Colorado, which consists of four large back-to-back gables.
At the First Congress of the International Association for Shell Structures, held in
Madrid in 1959, the Swiss engineer Heinz Isler presented a paper in which he illustrated
new techniques for creating nongeometric shell forms. This led to further explorations
into the expressive potential of concrete shells. Isler’s own design for the Sicli Company
Building (1969) in Geneva includes a flowing roof form supported at seven points. A
massive concrete shell in the shape of a Paleozoic trilobite roofed the Velodrome at the
1976 Olympics in Montreal. Although a major advantage of thin-shell concrete is its
usual low economic cost, the use of shells was a principal factor in the exorbitant cost of
the Sydney Opera House (1957–73) by Jørn Utzon. The complexity of the billowing, sail-
Encyclopedia of 20th-century architecture 562
like forms that compose its roof resulted in an engineering nightmare. It took
approximately 380,000 man-hours and 2,000 computer hours to complete the design.
During the last two decades of the 20th century, creative development in the design of
thin shells significantly waned. The few concrete shells that were constructed consist
primarily of simple cylinders and hemispheres on industrial buildings, such as bulkstorage
facilities. Milo Ketchum, a major designer of thin shells, suggested several
factors for the decline in an unpublished essay titled “What Happened to Shells?” His
reasons included the fact that the cost of concrete shells is usually more difficult to
calculate than the cost of precast, prestressed concrete slabs or steel roof systems, two
building forms that received extensive publicity in these years. Thin shells, in contrast, no
longer had a charismatic promoter, such as Tedesko or Candela, touting the benefits of
their use. As a result most engineers and architects were not fully aware of the aesthetic
and structural possibilities of concrete shells. Ketchum predicted, however, that sometime
in the future the relative cost of structural steel would rise to a point where once again
designers would be drawn to the aesthetic, structural, and economic benefits of concrete
shells.
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