New Ways of Naturally Bending Wood Are All About Curve Appeal

It normally takes an enormous amount of energy and heavy machinery to shape wood. Now, scientists have discovered a way of bending wood naturally: using digital tools that precisely define the shape in advance. This gives architects completely new, more sustainable outlooks for the future.

The Urbach Tower is situated on a small hill, surrounded by fields and vineyards in southwest Germany. Built as part of a horticultural show in 2019, the distinctive structure is a local landmark. The tower is also a manifesto for the future of architecture. Its curved wood facade is a paradigm shift in timber manufacturing. Instead of using elaborate wood-bending processes, the designers relied on natural forces to trigger the wood to more sustainably twist itself into shape with material programming.

Load testing has demonstrated that the self-shaping elements can withstand the same forces as conventionally shaped wood. Courtesy of ICD/ITKE, University of Stuttgart.

Visitors to the Urbach Tower can stand inside it. The tower offers shelter and warmth on the windy hill. Courtesy of ICD/ITKE, University of Stuttgart.

The roof of the tower is covered with a transparent layer that allows a glimpse of the sky. Courtesy of ICD/ITKE, University of Stuttgart.

The tower is the brainchild of two experts in the field: Dylan Wood, who leads the material-programming research team from the Institute for Computational Design and Construction (ICD) at the University of Stuttgart, and Markus Rüggeberg, from the Cellulose and Wood Materials Laboratory at Switzerland’s EMPA research institute, which created several wood projects as part of the innovative NEST building experiment in Zurich.

“Timber is a very sustainable material,” Wood says. “And it’s even more effective when it’s curved rather than straight.” Thanks to material programming, researchers have ensured wood can be made further attractive as a sustainable solution.

Computer Simulations Provide Precise Answers

To understand how material programming works, it’s important to start with the concept that, just as machines can be programmed to move in certain ways, wood can be “programmed” to deform in certain directions during the drying process. Computer simulations allow architects to preview wood deformations. This lets them know exactly how much material and moisture is required to achieve a certain shape.

The shaping process can begin once data such as desired material thickness and moisture content are calculated for a design. First, a thin dry layer of wood is glued on top of a thick, moist layer of wood, with their grains running at perpendicular angles. This process stabilizes the component so that when moisture is lost while drying, the wood shapes itself to the precise geometry that was previously determined by the computer-based process. Once the drying process is complete, the wood remains curved.

The prefabricated wooden parts of Urbach Tower were assembled on-site in a single day. Courtesy of ICD/ITKE, University of Stuttgart.

Drying is standard for producing both curved and straight wood in timber manufacturing. Courtesy of ICD/ITKE, University of Stuttgart.

The thinner the moist layer, the greater the curvature of the wood once the drying process is complete. Courtesy of ICD/ITKE, University of Stuttgart.

Complicating matters is the fact that the bent wood deforms as soon as it becomes wet again—in the rain, for example. To prevent the wood from distorting, several of these self-shaped layers of wood are glued on top of each other after the drying process.

The Urbach Tower, which was brought to life through a collaboration with structural engineers at the Institute of Building Structures and Structural Design (ITKE) at the University of Stuttgart, is the first large-scale structure in the world to use this new wood-bending process.

The tower comprises 12 spruce cross-laminated timber components, measures about 46 feet in height, and has a structural thickness of approximately 3.5 inches. “The geometry of the tower is so complex that we needed a complete BIM model as a common reference point for everyone involved in the project,” Wood says. He refers to the model as a “communication model” and explains that it proved particularly useful for coordination among different levels of contractors and on-site construction, allowing the prefabricated wood parts to be assembled in a single day.

To learn how bent wood reacts to changes in humidity and climate on-site, the researchers have also teamed up with the Swiss company ioLabs to monitor long-term data measurements using the Autodesk Forge platform. These findings are certain to be of use for the team at the University of Stuttgart as they plan to deploy the current shaping technology elsewhere.

No Assembly Required: To Self-Shaping Furniture and Beyond

The team is already developing new methods for self-shaping larger building components, like roof panels, directly on site. They’ve even recently unveiled a concept for flat-pack furniture that shapes itself at home with no assembly, tools, or instructions required.

“The beauty of these types of processes is that the digital tools allow us to embed shape directly into the materials of a component in the factory,” Wood says. “This could dramatically reduce the need for on-site machinery and the ecological impact of construction. It’s a cleaner and quieter method of building that could be widely distributed for projects where it’s too expensive to send out a team of workers or equipment. Instead, we direct the materials to do the complex heavy lifting.

“The best part is that here we can achieve this simply by understanding and directing a natural material. The researchers envision the concept as an ideal example of Industry 4.0: a highly flexible, adaptable manufacturing process based on the digitization, sorting, and arranging of natural materials to shape different geometries and products.”