| American Folk Art Museum
East 53rd Street, New York, N.Y.
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American Folk Art Museum
 The
American Folk Art Museum is a 7-story building that displays the
museum’s permanent collection and changing exhibits as well.
The goals of the project were to provide open spaces with natural
light on a constrained site and to create an image for a small museum
in the shadow of the larger Museum of Modern Art. Severud Associates
Consulting Engineers P.C. of New York City was the Structural Engineer
of Record for the design and Tod Williams Billie Tsien & Associates
Architects also of New York City were the primary consultant and
architect.
The museum’s second through fifth floors are devoted to gallery
space and are capped by a skylight above an atrium. The atrium allows
natural light to filter into the galleries and public spaces. Art
is integrated into the stairwells and walls of the museum by way
of a series of niches throughout the building. The building also
incorporates museum offices, classroom facilities, an auditorium,
a library and archive, a gift shop and a small coffee bar. The unique
bronze-paneled façade alludes to the folk art inside and
establishes the museum’s independence from the surrounding
buildings.
The overall budget of the project was $18.4 million. $4.1 million
was allocated for the structural portion of the project, which eventually
came in under budget at $3.9 million. Due to the use of exposed
architectural concrete, money initially designated for exterior
architectural finishes was transferred into the budget for concrete
work.
The Design
The unique and challenging nature of the museum became apparent
before the building ever rose from the ground. Adjacent to the museum,
the subway tunnel and subway ventilation room beneath 53rd Street
demanded a variety of accommodations. Heavily loaded adjacent footings
could not bear on the sub-grade rock within the influence line of
the subway tunnels. To bypass this problem a cantilevered foundation
bearing on steel-encased caissons was utilized. The caissons are
located seven feet North of the subway tunnel and are embedded into
the rock beneath the influence lines.
The design process of the building itself posed a variety of challenges
in accommodating the architect’s vision and the structural
integrity of the building. For instance, the 40-foot-wide site left
little space for circulation and light. Therefore, the bold decision
to pierce each floor with an atrium was balanced against the desire
to maximize exhibit space and floor-to-ceiling heights. Specific
requirements and site conditions pushed the engineering team to
apply innovative solutions to achieve these defined goals.
Initially, various structural materials were evaluated for their
suitability. The clear-spanning 40-foot width of the gallery with
a 30-foot span around the atrium made a steel frame appear to be
the best solution. However, this would have increased the depth
of the structural system, particularly when married with the mechanical
system. Fortunately, the architect was willing to leave the concrete
exposed, thus eliminating the need for the space-consuming fireproofing
and finish materials that the steel would have required. Formwork
was simplified by designing the floors as 16-inch-thick flat plates
rather than beams with soffits.
The exposed concrete adapted well as a finished building material.
Walls and soffits (where needed) where sandblasted to provide a
dull, matte finish, and floors were terrazzo-ground to expose the
concrete’s aggregates. An additional advantage of concrete
is its sound- and vibration-damping qualities.
 Concrete’s
ability to be sculpted was also employed in the construction of
the two interior stairs. The rear stair is a series of cantilevers
extending from the fifth floor down to the first floor mezzanine.
Each run of stairs has a torsion-reinforced, 8-inch-deep-by-2-foot-wide
spine that runs from the floor to the landing, across the landing,
and up to the floor above. A 4-inch-thick edge follows the steps
of the stair and extends out to the perimeter of each landing, completing
the appearance of a minimized structure.
Another concrete stair extends through the atrium. It is hung from
the edges of the atrium opening by concrete sidewalls. Construction
joint locations were selected to hide the construction-tell-tales
of the stair. Approximately 8-feet apart, the walls extend from
above the fourth floor to below the third floor. Each wall extends
over the edges of the floor slabs, and the construction joints between
floors in the wall slabs are hidden in reveals. Stair treads span
the 8 feet from wall to wall and were cast into wall keys to hide
their joints. With all of the construction joints hidden, the stair
appears to have been magically inserted into the concrete building.
 At
the building rear, a quandary of competing program and aesthetic
requirements was resolved with a concrete hanger. Achieving an open
main entry hall was complicated by the desire of the architect to
open a vertical slot along the back façade of the building.
With a slot running up the rear façade, a spandrel beam was
virtually eliminated from the third through fifth floors, and a
transfer girder located at the second floor would have obstructed
the entry hall. With the roof as the only suitable location for
the transfer girder, a hanger was required to support the floors
below. A structural steel frame was investigated for the rear of
the building, but it was determined that maintaining a reinforced
concrete system and leaving the rear of the building shored until
the roof was cast and cured would be more cost effective. Furthermore,
the reinforcing in the concrete hanger was designed for both strain
and strength. Reinforcing just for strength would not eliminate
visible cracks in the hanger under full load. By increasing the
amount of steel reinforcement, the strain in the hanger under full
load is kept below the strain at which visible cracking occurs in
concrete, thus eliminating visible cracks.
 The
bronze facade of the American Folk Art Museum is designed to make
a strong but subtle statement of independence from the Museum of
Modern Art. The façade is sculptural in form and folded into
faceted planes of bronze and glass. The three major planes of the
façade are composed of white-bronze panels that were “spill-cast”
against the foundry’s concrete floor. The bronze panels and
planes catch the glow of the sun as it rises and sets, east and
west along 53rd street.
Spill casting produced panels with a mottled surface and exposed
cold seams, but also panels that are inconsistent and which defy
specification. Representative test panels were cast and tested to
produce design parameters that were then applied to the façade.
Ultimately, the panels were welded onto steel frames to provide
additional stiffness and connection points. Originally, the idea
was to provide another steel frame on the face of the building to
receive the panels; however, a cost-savings was realized by building
a backup wall with heavy 6” studs and plywood sheathing.
Planes of curtain wall make a recessed reveal along each side of
and beneath the panels to lighten the façade and make the
planes of bronze appear to float above the entrance. Though the
16-inch slab is sufficient to carry the weight of the floor and
façade across the 40-foot southern face of the building,
early analysis showed that the relative live load deflection and
the creep of the concrete would drive the size of the joints between
panels up to 2 inches. Unwilling to accept joints of this size in
the façade, the design team instead installed a “post”
in the middle of the front façade. A single, true column
was initially proposed, but its size was considered an intrusion
to the appearance of the floating façade, particularly since
it would be the only concrete element among surfaces of metal. As
a result, three smaller stainless steel pipes, which don’t
stand out awkwardly and which keep the façade panels square
and true, were installed. The super-structure and foundations were
designed to perform with or without the steel pipes so that they
could be left exposed.
By developing innovative solutions, the design team was able to
produce a building that realized the architect’s vision and
was economical. With attention to program, efficiency, economy and
site constraints, the design team provided effective solutions to
the unique and varied challenges involved in the museum’s
design. The American Museum of Folk Art demonstrates engineering
excellence coupled with the advantages offered by architectural
exposed concrete.
The American Folk Art Museum was selected "Best New Building
in the World for 2001" and in October 2002 the building was
awarded the prestigious Brendan Gill Prize by the Municipal Art
Society of New York. It also won the 2003 award for engineering
excellence from the New York Association of Consulting Engineers
(NYACE).
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