Located in the National Mall in Washington, DC, the $200-million National Museum of the American Indian opened to the public on September 21, 2004. The 210,000 square foot, five-story museum, expected to be the last Smithsonian facility built in Washington, DC, evokes nature with its stone cladding façade intended to resemble a solid piece of weathered rock. Contractors faced challenges building the structure, which incorporated a curvilinear form on a 4.25-acre trapezoidal site that sits atop an active creek bed. One design highlight includes crystal prisms, installed facing south to catch the sun’s rays, that reflect the continually changing light spectrum.
Concrete framing using flat-plate construction helped in keeping the floor-to-floor height at a minimum, thereby maximizing the number of floors while remaining within the Capital’s maximum building height restriction of about 130 feet. The ability to locate building frame columns in a “shot-gun” layout allowed the architect the flexibility to change column locations to accommodate architectural requirements while maintain the structural integrity of the frame. This type of column placement essentially means that columns do not have to line up between floors and the vertical load transfer is achieved by “walking the load” thru the slab from the column above to the column below.
Another key advantage of conventional flat plate systems is the reduction of floor to floor heights which significantly reduced the cost of formwork and building frame. Because of simplicity in construction; the flat plate lends itself to the use of conventional formwork while the lower floor to floor heights allows for the use of conventional stick shoring.
One of the main features of this structure is its exterior form which consists of a combination elliptical curves that change both shape and location between floors. The architect’s design called for a stunning tan building, layered in swooping levels of Minnesota limestone rounded to depict the curves of the earth, sun and moon. The ability to economically construct this type of “flowing” building facade was achieved by the fact that cast-in-place concrete can be easily formed and placed to achieve the desired effect. A complex shape of this nature inevitably requires a tremendous amount of coordination between all building trades and field changes during construction are unavoidable; however, concrete was also viewed favorably in this aspect because field changes were faster which minimized project delays.
Douglas Cardinal Architect Inc., Ottawa Ontario Canada
Severud & Associates, New York, New York