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By Claude Goguen, P.E., LEED AP
As the sustainable building movement continues to evolve, so have its architectural design possibilities. Incredible edifices are being constructed all over the world that are environmentally conscious and resource-efficient throughout their life cycles. A shining example of this trend can be found in Victory Park near downtown Dallas. The large, striated cube made of precast concrete and glass that seems to float in mid air houses the new Perot Museum of Nature and Science, and it is a breathtaking sight to see.
Opened in December 2012, a month ahead of schedule, this $185-million project was designed by Thom Mayne, a Pritzker Architecture Prize laureate. The tower, the largest part of the museum, is made up of 70,000 sq ft of precast panels; a plinth section consisting of 220 panels, or 27,000 sq ft of curved panels; and the atrium inside the tower containing 100 panels.
Gate Precast supplied the precast concrete architectural panels. A case study on the Gate website states that, “The 180,000-square-foot museum was designed to resemble a sedimentary geological formation. The precast concrete facade satisfies the intent to reflect the geology and stratification of the earth’s surface through the creation of undulating forms, which are rigorously systematic but seemingly random.”
Gate Precast worked with the design team to define the cladding through the creation of mock-ups with varying horizontal striations. The panel design incorporates both convex and concave horizontal striations. “The random combinations lend striking shadows, and the striations give way to smooth concrete surfaces on higher levels of the building,” according to the case study.
For the cube portion of the building, precast concrete panels averaged 8 ft tall and 28 ft long with alternating 20-degree sloped ends. “The plinth panels were curved, canted and radiused to follow a serpentine path around the site,” the case study states.
According to the architect, the precast facade “minimizes the use of material through a systematized, standard panel that maximizes modularity, interchangeability and the appearance of a complex, dynamic facade.” The panels were designed and organized into categories of forms or families from which rubber molds were created.
“The resultant precast concrete facade satisfies the intent to reflect the geology and stratification of the earth’s surface through the creation of undulating forms, which are rigorously systematic but seemingly random,” the case study said.
Installation of precast on this project was meticulous even with extensive planning. Erection of the precast panels was painstakingly slow due to the amount of survey work required prior to setting each individual panel to ensure the structure itself was correct. The unconventional methods used to erect such complex pieces also added obstacles. About five panels were erected per day on the tower, two per day on the plinth area and one per day in the atrium area.
Due to the curvature on so many different panels, the precaster’s engineering department was required to provide a “face of panel” dimension to each corner of every panel so that the surveyors could locate exactly where the panel face should be in its correct erected position.
Erection and aesthetic tolerances take on a new meaning on the plinth panels, which track around the site perimeter. This wall of precast runs for approximately 1,400 lineal ft and includes 25 different points of radius along its journey.
The precast staging area was “large enough to stage three to five trailers near the tower, making erection as efficient as possible,” according to an article on the museum in ENR Magazine. Due to the sloped ends of each panel, erection could proceed only in one direction around the building so that the panels could be installed one under the other more easily.
The building was able to achieve LEED Gold certification. This achievement was aided by the use of concrete panels that incorporated recycled materials and that were manufactured locally to satisfy the Regional Materials credit. There was no waste generated on site as the panels were fabricated at the plant and shipped to the site, ready to install. The use of precast concrete also contributes to minimizing energy due to its thermal mass.
This museum is truly a testament to the versatility of architectural precast concrete. Its impact will be felt by many generations of families who enter its doors, but not by the surrounding natural environment thanks to forward-thinking designers and manufacturers.
Claude Goguen, P.E., LEED AP, is NPCA’s director of Technical Services.