Joshua Tree, California
By pushing the structural capabilities of straw-bale construction, we helped to create a high-performance retreat that blends with the desert landscape.
The late composer Lou Harrison sought a retreat in Joshua Tree that would provide superior acoustics for his work, while also reflecting his commitment to the environment. Because Joshua Tree is located in a high seismic zone, the structure also needed to withstand severe earthquakes. Architecture firm Skillful Means approached us to redesign the structure after a conventional design proved too costly.
To meet the budget, we had to utilize the structural capabilities of straw bales and, in so doing, create a new structural theory for straw-bale performance. In contrast with most straw-bale structures, which use the bales as insulation wall finishes only, in the Harrison residence the bales serve as the primary structural elements, supporting all gravity and seismic loads. The composite construction consists of straw bales, wire mesh, and stucco. The design theory is a synthesis of stress-skin-panel and reinforced-concrete behavior models. It also recognizes straw’s energy-absorption characteristics to provide exceptional ductility under severe seismic loading.
The most vexing problem was the barrel-vaulted, column-free great room. Since the stiff skins are continuously braced from buckling, models used for stress-skin panels could be adapted to design for flexural loads. The reinforced-concrete strut-and-tie mechanism was modified to address shear loads in the vault. To validate the design concepts and gain approval from a skeptical building department, the team tested a full-scale, four-foot-thick “slice” of the vault, using a rig to simulate seismic effects. The structure remained stable as it was loaded well into the plastic deformation range, far exceeding building-code strength requirements. The test results, along with an independent peer review, secured the building department’s approval for this radically new structural system.
Executed as Tipping Mar
2004 U.S. Green Building Council Presented Poster Competition, Award of Merit
2002 SEAONC Excellence in Structural Engineering, Award of Excellence