"The Ingalls Building, built in 1903 in Cincinnati, Ohio, was the world's
first reinforced concrete skyscraper. The 15 story building was designed by the
Cincinnati architectural firm Elzner & Anderson and was named for its primary
financial investor, Melville Ingalls. The building was considered a daring
engineering feat at the time, but its success contributed to the acceptance of
concrete construction in high-rise buildings in the United States.
The Ingalls building is bordered by East 4th Street and Vine Street in the
Cincinnati Central Business District.
Overcoming skepticism
Prior to 1902, the tallest reinforced concrete structure in the world was
only six stories high. Since concrete possesses very low tensile (pulling)
strength, many people from both the public and the engineering community
believed that a concrete tower as tall as the plan for the Ingalls Building
would collapse under wind loads or even its own weight. When the building was
completed and the supports removed, one reporter allegedly stayed awake through
the night in order to be the first to report on the building's demise.
Ingalls and engineer Henry N. Hooper were convinced, however, that Ernest L.
Ransome's system of casting twisted steel bars inside of concrete slabs as
reinforcement (patented in 1884) and casting slab, beams and joists as a unit
would allow them to create a rigid structure. The architects also prized the
cost savings and fireproofing advantages of concrete over steel frame
construction. Finally, after two years of convincing, city officials issued
Ingalls a building permit and the work began.
Construction
Hooper
designed a monolithic "concrete box of eight-inch [200 mm] walls, with concrete
floors and roof, concrete beams, concrete columns, concrete stairs -- no steel.
It consists merely of bars embedded in concrete, with the ends interlaced."
(Ali)
The amount of concrete produced during construction -- 100 cubic yards (76
m³) in each ten-hour shift -- was limited by the rate at which the builders
could place it. An extra wet mix was used to insure complete contact with the
rebars and uniform density in the columns. Floor slabs were poured without
joints at the rate of three stories per month. Columns measured 30 by 34 inches
(760 by 860 mm) for the first ten floors and 12 inches (300 mm) square for the
rest. Three sets of forms were used, rotating from the bottom to the top of the
building when the concrete had cured. Completed in eight months, the finished
building measures 50 by 100 feet (15 by 30 m) at its base and 210 feet (64 m)
tall.
The exterior concrete walls are eight inches thick (200 mm) in unbroken slabs
16 feet (5 m) square with a veneer 4 to 6 inches (100 to 150 mm) thick. The
Beaux Arts Classical exterior is covered on the first three stories with white
marble, on the next eleven stories with glazed gray brick, and on the top floor
and cornice with glazed white terra cotta.
Landmark status
Still in use today, the building was designated a National Historic Civil
Engineering Landmark in 1974 by the American Society of Civil Engineers. In
1975, it was added to the National Register of Historic Places." ~ Wikipedia