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New York, New York
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A New Landscape for Reinforced Concrete Office Towers in New York
City
 This
$62 million, 10-story office building in Manhattan’s Chelsea
District will serve as the East Coast headquarters of IAC/ InterActiveCorp,
a prominent multi-media firm. Designed by renowned Architect Frank
Ghery, the building is located between 18th and 19th Streets, across
from the Chelsea Pier in Manhattan. The gross area of the building
is 550,000 square feet which includes retail space in the lower
floors and typical office space above the 7th floor. The building
is reminiscent of the boat sails on the adjacent Hudson River. The
billowing exterior curtain wall was sculpted with a glass-façade
to produce dramatic angles and spectacular views for the interior
office spaces.
To accommodate this untraditional architectural design; the structural
engineering office of DeSimone Consulting Engineers of New York
City designed a gravity defying concrete frame with a typical 12-inch
flat-plate concrete floor with spans up to 35 feet. Only two columns
are truly vertical. All other columns have some degree of inclination—up
to 25 degrees from vertical. The reinforced concrete shear walls
in the core counteract the twisting effect of the columns to stabilize
the structure. The floor slabs also include numerous openings which
offer interior views of the building.
A key advantage of conventional flat slab systems is the reduction
of floor to floor heights which significantly reduced the cost of
formwork and building frame. The flat-slab lends itself to the use
of conventional plywood construction while the lower floor to floor
heights allows for the use of conventional stick shoring.
 Building
each floor on a two-day cycle is facilitated by selecting this floor
system with its offer of the simplified formwork. While an aggressive
construction schedule, the two-day cycle is the preferred method
of construction in New York City. A trend set in the late sixties
and made possible by the moderate spans and lower floor to floor
heights common in residential hi-rise flat-plate construction. Unprecedented
in office building construction, the two-day cycle will reduce the
floor completion schedule by 50% compared to an equivalent structural
steel floor system.
The lateral force resisting system efficiently incorporated the
12” flat-slab with a 12" thick concrete shear wall which
completely encases the fire stair above the mezzanine floor. Managing
the eccentricity created by the gravity defying frame, the shear
wall elements located at the core of the building was easily accommodated
without the need for additional structural element. 5000-psi concrete
was used throughout the structure.
Cast-in-place concrete construction provided the building with
better acoustic properties, fireproofing at no additional cost and
enhanced robustness in the event of unusual loading events or terrorist
attacks. The 12-in. concrete shear wall completely encasing the
fire stairs is a significant safety feature of this structure. With
minor additional engineering effort and cost to the owner, concrete
structures have always been considered the natural solution to anti-terrorism,
force protection and fire resistance.
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