BENTONVILLE, AR – Surrounded by 120 wooded acres, Crystal Bridges Museum of American Art is set to open tomorrow, November 11, 2011. Comprised of a series of eight concrete, glass, and wood pavilions set along two spring-fed ponds in Northwest Arkansas, this architectural vision was designed by Safdie Architects. Multi-disciplinary engineering firm Buro Happold provided the structural and MEP engineering that brought this innovative museum complex to life, including the engineering of several cable-supported timber roofs of unprecedented design.
Founded in 2005 by the Walton Family Foundation, the new museum is a union of art and architecture in a striking natural setting. This 201,000-sq.-ft. building takes its name from the nearby Crystal Spring, and houses galleries, meeting and classroom spaces, and a large glass-enclosed gathering hall.
The architectural vision to create suspended buildings created numerous challenges for the engineers and required innovative design solutions to realize. Buro Happold used bridge technology to create suspended roof structures and custom-built structural beams that are made from locally sourced and fabricated glulam (glued laminated pine timbers).
“In order to create the complex structures, we used traditional, local materials for structural elements, combined with state-of-the-art technology, which allowed us to develop our sophisticated engineering solutions with precision,” explained Craig Schwitter, PE, Buro Happold Managing Director for North America and Principal-in-Charge for Crystal Bridges.
Buro Happold approached the plans for the suspended buildings by adopting bridge construction methodology. By analyzing computer-designed models, the team was able to determine the best form for the hanging structures: a series of cable-supported timber roofs. They also developed a digital model of the roof to help the contractor build these complex geometric structures. The models allowed a high degree of accuracy in the fabrication of glass, steel and cable components.
While glulam arches are typically curved in one direction, for this project they had to curve in both directions to create the double curvature of the roofs. The connections between these glulam beams and the cables were also of high importance. Buro Happold devised a universal ball and socket connection that accommodates some movement in the geometrically irregular building, and so was able to withstand changes in geometry that occurred during construction.
The roof design was based on the catenary shape of the cable under its load, and so was driven by physics rather than architecture. Buro Happold used the state-of-the-art computer software CATIA to model the suspended bridge roofs, which are composed of paired, 4-inch steel catenary cables separated by beams made from glulam.
The suspension of the central roofs also required an intricate level of attention to the anchoring of the building supports, which was made more challenging by the creek bed. To secure the buildings, Buro Happold installed anchors in the limestone bedrock to stabilize the large abutments at each end of the roofs and support the cable network.
The location’s creek bed also needed to be dammed to create the two ponds, and the water must be kept at a controlled level all year round. Waterproofing the buildings was a key issue, as it was mandatory for the conservation of artwork within the structures. Buro Happold used minipile technology to reduce the foundation depth in the weathered limestone and stabilize the site.
Buro Happold seamlessly integrated the building’s MEP systems within its complex structure. The engineers used thermal modeling and computational fluid dynamics to model the galleries and conference hall and devise means of concealing the MEP systems to maintain the slender profile of the roofs and buildings. This allowed them to hide the HVAC systems, which include radiant floor heating and cooling systems. Buro Happold also installed sound attenuators to reduce noise and allow for a serene, undisturbed gallery environment, while the HVAC system provides meticulous climate control for the galleries, keeping them within a two degree Fahrenheit and five percent humidity range.
Client: Crystal Bridges Museum of American Art
Architect: Safdie Architects
Services provided by Buro Happold: Structural and MEP engineering