A New Landscape for Reinforced Concrete Office Towers in New York City (2007)

IAC_renderingThis $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 seventh 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.

IAC_constructionBuilding 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 1960s 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 percent compared to an equivalent structural steel floor system.

The lateral force resisting system efficiently incorporated the 12-inch flat-slab with a 12-inch 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. 5,000-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-inch 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. 



Owner Representativeand Construction Manager:
Turner Construction, Chicago, Illinois

Frank Ghery

Structural Engineer:
DeSimone Consulting Engineers, New York, New York

Concrete Hi-Rise Contactor:
Sorbara Construction, Lynbrook, New York

Superstructure and Foundation Concrete Supplier:
Quadrozzi Corporation, Far Rockaway, New York