During last year’s International Mass Timber conference, the most eye-catching component of the pavilion was a soaring space frame built using tubular veneer timber, a material developed by UO researchers Dr. Dylan Wood and MS student Helene Brehl. This year, the team integrated that technology into a prototype for an ultralight mass timber floor slab serving as a dancefloor for conference goers to enjoy.
Tubular Mass Timber Dancefloor
Dr. Dylan Wood
Assistant Professor of Architecture
University of Oregon
Helene Brehl
Masters Student
University of Oregon
The prototype floor employed the hollow veneer-based tubes as its primary structural element sandwiched between the two one-inch thick Mass Plywood lamella supplied by Freres Engineered Wood and connected using XEPOX Epoxy Adhesives from Rothoblaas. Combined, the floor panels use less than a quarter of the fiber and mass of conventional mass timber floor panels and can be easily tuned for both structural and acoustic performance. The larger dance floor was also instrumented with accelerometers, allowing dancers to see how their movements impacted the structure while also giving the team the opportunity to complete basic vibration testing live at the conference.
The veneer tubes are part of an ongoing research project that takes advantage of wood’s natural moisture-based shrink and swell cycles, a feature that generally challenges wood products manufacturers. They are made from a two-layer plywood, specifically Douglas Fir and Maple layers with PUR adhesives from Henkel AG. As the panel dries out, the wet ply gradually shrinks and panel naturally rolls out into a whole hollow tube – a surpringly strong shape for how little material is needed.
Brehl began working on this project as an undergraduate researcher with Dr. Wood, whose previous work includes the design and construction of several structures that leverage wood’s ability to change its shape depending on its moisture content. Initially, her work focused on developing a method to consistently produce tubes and determine how variable the curvature of the final product would be. As progress grew, Brehl also completed some preliminary compression testing with the assistance of Dr. Wood and Dr. Erica Fischer of OSU’s College of Engineering.
From there, Brehl explained, the next phase was clear, “[Once] we knew that these tubes curl to a certain diameter, and that they’re light, and they’re also really strong from how much fiber is used in them, we looked at what we could actually do with them to be useful.”
Several potential uses are being investigated, but the research team ultimately settled on developing a hollow core cassette panel that could potentially act as an ultralight floor panel. The team took inspiration from the aluminum honeycomb panels that are widely used in aeronautic applications – where weight is the most significantly limiting factor – for the design and adapted it for a mass timber context. As seen on the dancefloor, the cassettes are formed from MPP top and bottom layers with short, vertical segments of the wood tubes sandwiched between them. The wood tubes have a particularly high strength in compression when stood on their end.
“Current systems like conventional CLT or MPP floor panels have so much mass in them, and its not necessarily where the structure is needed. In floor panels, the top and the bottom of the panel take most of the force and the center isn’t doing very much. It adds depth, which increases the span of the panel, but it’s not doing most of the structural work. The panels that we’re making use much less material in the center, which produces an overall lighter panel and a lower load on the structure overall.”
Helene reported that the reception to the panels by conference goers was generally positive. “A lot of people remembered the tube research from last year and the year before.” It was exciting to be able to discuss the progression of the work, from an abstract idea based on the unique features of wood, to a demonstration piece, to a conceivable – if far off – product.
To begin to understand these properties, the researchers took advantage of the live instrumentation on the dance floor to conduct a footfall test, and they will continue testing them in different contexts as research progresses.
As every year passes, TDI finds itself more grateful for opportunities to showcase our cutting-edge mass timber research to those across the Pacific Northwest. Thanks to the ongoing support of our faculty contributors at Oregon State University and the University of Oregon, student volunteers, and our staff at the lab, we are excited for what’s to come.
