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This Wooden Tower Twisted Itself Into Shape With New Drying Process

Researchers at the University of Stuttgart’s Institute for Computational Design and Construction are experimenting with wood in a very interesting way. They are investigating a method of how to manipulate the typical behavior of wood to warp as it dries in such a way that it works for, rather than against the materials structural integrity. In essence, they are developing a way in which the process can actually be harnessed for more efficient construction.

From this idea, the team manifested a magnificent 14 meter (45-ft) tall tower made up of timber pieces that twisted themselves into shape! They say their Urbach Tower is the first structure in the world to use self-shaped building-scale components.

Team member and doctoral candidate Dylan Wood said:

The elegant part here is that we don’t need to add water as wood cut starts with a high moisture content, so in a way we are just strategically intervening in the drying process to use the shrinking forces rather than fighting them.

To prepare timber for construction, it has to be rid of moisture. This is done by drying it out in a kiln, or a machine with similar heating capabilities. The procedure causes the wood to deform, but ultimately stabilizes it and makes it suitable for use. This is the exact phase of the wood preparing process that the researchers are toying with. By interfering in this part of the process they can “program” the wood so that it transforms into desired shapes, just like you might program a robot to perform particular movements. The Urbach Tower was made like this then finished with a protective facade of larch wood to prevent further warping.

Wood explained:

By carefully understanding and digitally modeling the deformations that occur in the drying process we can arrange the wood before drying to produce specific deformations. More specifically, we build flat wood bilayers plates (two layers with opposing grain directions) while the wood still has a relatively high moisture content. The plates are dried using industrial drying processes and they emerge curved. The species of wood, grain orientations, thickness ratios, and the change in moisture during the drying process are all parameters that affect the curvature.

How They Did It

  • First, the bilayers were produced to contain 22% wood moisture content and were then dried to 12% (standard for this type of construction). As they dried, the pieces took on their curved shape.
  • Next, the bilayers were stacked and glued together to lock their curvatures in place.
  • Then, the warped Cross Laminated Timber (CLT) components were transported by truck to a site at Remstal Gartenschau 2019 (a garden show in the German city of Schorndorf).
  • Once all the pieces were on site, it took a team of four craftsmen only one day to assemble them into a tower.
  • Lastly, they topped the tower off with a transparent roof and finished it with a protective facade of larch wood.
  • The tower is even equipped with sensors that will track moisture content over the coming decade to try to keep tabs on any further warping.

This process can theoretically be applied to any species of wood, as it all shrinks and swells, although Wood and his colleagues used spruce wood boards sourced from Switzerland. The researchers hope that the Urbach Tower will serve well as a proof-of-concept for a form of self-shaping architecture that can make wood a more appealing material for different kinds of projects.

As a bonus to its beauty, structures such as this are better for the environment and cost less. For one, the material (wood) is more sustainable than concrete or steel; and secondly, contorting the wood into desired shapes through this method negates the need for energy-intensive mechanical forming that involves serious machinery because the material itself is doing the heavy lifting. Without the need for mechanical forming, the cost goes down making these kinds of curved CLT pieces a viable option for load-bearing components in walls and long roof structures.

However, the technology is not just limited to building components! It could even extend beyond the world of construction. Wood said:

Our research group at ICD is also studying similar self-shaping methods using wood and new materials combined with 3D printing where we can tune the shapes and speed for smaller parts with more complex movements. These parts have a range of applications, from building facades and roofs that open and close autonomously with the weather to clothing that vents when you sweat and seal when you are cold.

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