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Project in Detail

Eight Spruce Street

Structural Design - Towers
United States of America
Gehry Partners, LLP
2011
World Architecture Festival 2011 - Structural Design of the Year

Beekman Tower 


The 867 ft, 76-story iconic Beekman Tower, designed by renowned architect Frank Gehry, is New York City’s tallest residential tower. Located in the middle of the block bounded by Nassau, Beekman, Spruce and Gold Streets, just south of the Brooklyn Bridge, the 1.1 million SF mixed-use building has redefined the skyline of Downtown Manhattan. The tower offers 903 high-end residential units, luxury amenities and unobstructed 360 degree panoramic views and sits above a 100 foot tall, 6-story podium that comprises a new 100,000 SF public school as well as a 21,000 SF ambulatory care center for New York Downtown Hospital.

The building’s main aesthetic is its undulating, asymmetrical steel curtain wall with curvaceous folds and crinkles reminiscent of the folds in a piece of gently draped fabric. The sculptural façade is comprised of stainless steel and glass panels and gives the building a sense of movement; however Mr. Gehry’s “Bernini folds” conceals a multitude of challenges successfully met through the implementation of innovative structural engineering solutions.

Beekman Tower is a reinforced concrete building. The structure is composed of cast-in-place, concrete flat plate floors supported by reinforced concrete columns and shear walls. The 5 to 6 ft deep mat foundation is supported on 18” diameter concrete encased steel piles and also various capacity drilled caissons adjacent to an MTA subway tunnel.
The lateral wind and seismic resisting system is composed of reinforced concrete shear walls surrounding the building’s core. For increased system efficiency, outrigger walls are introduced at mechanical floor levels 6, 38 and 76. The outrigger walls engage the perimeter columns augmenting the lateral system substantially. These concrete walls were carefully located to minimize the impact of the mechanical equipment functions. The fact that all the shear walls are centralized around the core with no walls dissecting the typical residential floors, provided the architect/developer great design opportunities unobstructed by the structural elements. The outriggers and their associated belt wall system have a huge effect in reducing the building drift as well as the base moments due to lateral forces. This helped reduce the thickness of the shear walls and ensured an extremely efficient system. In addition, in order to further provide adequate lateral stiffness and minimize architectural impact, high strength concrete of over 12,000 psi was specified for the shear walls and columns whereas the specification for slab concrete ranged from 5,000 to 8,600 psi.

The outrigger walls were also used as transfer structures for the exterior columns. The building stacking changes at the outrigger floors and most of the exterior column pickups are undertaken by the outriggers to maintain efficiency of internal space.

A further unique challenge of axial shortening had to be met. Studies were performed and over pour values were specified for casting the columns in order to mitigate the effect of differential axial shortening between the core walls and the columns not just for the final construction condition but also for the construction sequencing stages.

The structural challenge of accommodating the undulating façade, as well as the differing apartment layouts has been met by ‘walking’ the columns at several locations and levels. No tower floor plates are alike and slab edges are in different planes on every floor, however in order to simplify the formwork, columns were designed and constructed to stay in the same plane for about every eight to twelve floors. At the ‘change’ levels, the columns broaden or ‘walk’ to encompass the column location above and below. This strategy, apart from avoiding the use of transfer beams, also avoided sloping the columns which would have required more complicated and laborious formwork while also maintaining the construction rhythm. In addition, 3-dimensional CAD detailing was undertaken to design the formwork for the undulating slab edges and maintain the sculptured edge detail of the concrete floors.

Furthermore, all forms were hand-set because the layout changed so much and because slab edges are segmented and protrude. Indeed, exact placement of the 14,000 curtain wall embeds on the segmented slab edges was critical to correctly anchor the façade units and keep the construction on schedule.

The rectilinear podium is clad in terracotta-colored masonry and design was coordinated closely with the school architects (Swanke Hayden Connell) to ensure an optimum layout, bearing in mind that it is basically supporting 72 stories above. Larger clear spans of up to 35 feet with 10” to 12” flat plate floors were utilized to accommodate the school and hospital architectural layouts as opposed to the shorter spans using 8” flat plate floors within the residential spaces above.

Beekman Tower’s dramatic interior lobby is adorned with colossal oval-shaped concrete columns. These unique elliptical members were created by using custom-designed, 19 foot tall, fiber-reinforced polymer (FRP) column forms to create their imposing presence and beautiful aesthetic finish.

The site is tightly bound on all sides by a hospital, a university, two landmark historic buildings and a subway tunnel. Construction logistics met these challenges by continuously having two concrete trucks available in the building’s west plaza (which was designed to carry their loads) for continuous pouring. The construction team managed to keep to a 2-day cycle at the highest floors by pumping concrete all the way to the top of the building. Furthermore, full coordination and communication was maintained with the appropriate authorities to successfully meet the challenges of the major upgrading being undertaken to surrounding streets as well as the proximity of the subway tunnel.

Foundation work started in October 2006 and work on the superstructure began in April 2008. The building topped out in November 2009 and the project was completed under budget and on schedule in spite of a 3 month work hiatus related to the recent recession. The Public School is due to open in September 2011 and residential leasing and occupancy began in February 2011. The fast construction of this unique and iconic building is testament to the overall team's efficient design and construction planning.

Lead Architect »

Gehry Partners, LLP
 

Professional Credits »

Architect
Gehry Partners, LLP
United States of America

Client / Developer
Forest City Ratner
United States of America

Environmental Engineer
Mueser Rutledge Consulting Engineers
United States of America

Main Contractor
Kreisler Borg Florman
United States of America

Structural Engineer
WSP Cantor Seinuk
United States of America