Carapace Pavilion in Joshua Tree National Park transforms what would usually be considered an unsightly structure into a modern work of art.
The project is a prototype replacement enclosure for the standard double-restroom buildings used widely throughout state and national parks. When the idea for the project emerged, the designers knew they needed a material that would be both flexible and durable enough to withstand the extreme desert climate of Joshua Tree.
“The sun is intense in a nearly cloudless sky at 4000 ft above sea level, and it can freeze overnight,” says Doug Noble, associate professor of architecture at USC School of Architecture and codirector of the Clipper Laboratory for Architectural Computing.
The structure also had to be designed for the high-seismic environment, and because it is in a national park, upkeep and repair requirements had to be minimal. “We needed a material that required little or no maintenance for many years and could take decades of neglect in a tough environment,” Noble says. “Precast concrete was the only possible answer.”
Noble worked with USC professor Karen Kensek, an expert in the field of computer applications for architecture, to design a precast concrete structure that could meet all requirements while blending effortlessly into the curvilinear forms and colors of the natural rock landscapes in the park. Noble and Kensek also engaged many of their architecture students in the project as a unique learning opportunity.
“Every chance we got, we added layers of difficulty so the students could learn how to really work with engineers, precasters, and concrete material,” Noble says. “We wanted everyone to help work the design and material.”
Zero maintenance, seismic resistant
The design is composed of one foundation panel, two identical wall panels, and two identical roof panels. The team used custom software scripting to guide the parametric requirements, incorporating a double-curved geometry with a diagrid structure. The use of ultra-high-performance concrete (UHPC) allowed development of a shell that is only 2 in. thick at the most structurally significant section along the panel centerlines.
“We wanted it to push the capabilities of the precast concrete material as far as we could,” Noble says. “Having UHPC only 2 in. thick was a deliberate design decision.”
The panels were assembled based on rotational symmetry. Using finite element analysis (FEA), the team pursued an extreme overhang, with the roof measuring 42 ft and extending well beyond the 12 ft foundation panel. Interior diagonal bracing and shear walls were avoided by using stainless vector connectors in a staggered moment-frame configuration.
The ultimate design blends elegantly into the landscape and leaves a light touch on the land. “The raised plinth and earth-anchor strategy avoids significant disturbance to the site and protects potentially sensitive native cultures’ artifacts,” Noble says.
The design team expects the structure to achieve a life span of more than 100 years with effectively zero maintenance. “We know a major earthquake is likely happen at this site in the next 100 years,” Noble says. “The Carapace Pavilion will be able to withstand that, so it will still be there well into the next century.”