Award: Stereoform Slab’s Optimized Structure Reduces Embodied Concrete

In an effort to improve upon the carbon footprint of the ubiquitous flat plate, the Chicago office of Skidmore, Owings & Merrill and Odense, Denmark–based formwork robotics firm Odico jumped straight to revolutionizing the form of the slab itself. They then demonstrated the potential of their innovation—Stereoform Slab—in a full-scale prototype.

“We wanted a structural solution to minimize the amount of material [used] to reduce the embodied carbon,” says SOM design partner Scott Duncan, AIA. “We wanted it to be implementable at scale, readily constructible, and no more costly than a conventional system.” Typical reinforced concrete structures incorporate 10- to 12-inch-thick plate slabs, which, though simple to build, require more concrete and rebar than other slab configurations, Duncan says. The Stereoform Slab system is a mere 6 inches thick, and is supported by a “smart band beam” whose tapering form, optimized through computational design, efficiently transfers loads to columns spaced 45 feet apart, for a floor plan with 30-foot bays. “We’re able to achieve longer spans than a conventional flat plate, which means fewer columns [and less] concrete in the foundations of the building,” Duncan says.

SOM began designing the Stereoform pavilion about six months before its debut at the 2019 Chicago Architecture Biennial. Odico used a robotic hot-wire cutting technique to make the expanded polystyrene (EPS) formwork. This technique is much faster than CNC milling, says Odico chief technology officer Asbjørn Søndergaard, though it limits the form to “ruled surfaces,” which must be defined by the straight line of the cutting wire. EPS is a petrochemical plastic product, Søndergaard acknowledges, but the EPS formwork takes less energy to produce than wood formwork and can be “almost 100%” recovered and recycled.

To make concrete beautiful like this, you have to build the formwork like cabinets.

—Juror Steve McDowell, FAIA

The resulting 70-foot-long, 24-foot-wide, 14-foot-tall pavilion, a potential module in a multistory structure, was erected in less than a week by a concrete contractor and uses 20% less concrete than a conventional slab with the same load capacity, according to SOM and Odico. The expressiveness of the structure adds to the Stereoform Slab’s appeal, Duncan says: “Our clients are drawn to the authenticity of exposed ceilings, higher ceiling heights, and the loft aesthetic.”

Stereoform’s captivating form, comparable strength, and competitive cost add to his conviction: “We’re committed to reducing embodied carbon and implementing this at scale,” he vows. “You have my word. We’re going to make it happen.”

Project Credits
Project: Stereoform Slab
Architect: SOM, Chicago . Scott Duncan, AIA (design partner), Benton Johnson (structural director), Adam Semel, AIA (managing partner), Ryan Culligan, AIA (design director), Jonathan Baranowski, Austin Devin, Turner Solterman, Martin Rauber, Assoc. AIA, Kyle Vansice, Rahul Attraya
Collaborating Partners: Odico, McHugh, Sterling Bay, Autodesk

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