Construction wood that bends itself

Researchers have developed a new technique that allows wooden panels to bend into a pre-set shape without the use of external mechanical force. This makes it possible to construct complex architectural designs out of a sustainable construction material.

Wooden building elements can now be bent into a pre-set shape without the use of any mechanical force thanks to the efforts of researchers at the Federal Institute of Technology (ETH) in Zurich, the Swiss Federal Laboratories for Materials Science and Technology (Empa) and the University of Stuttgart in Germany.

In a study recently published in Science Advances, the researchers show how solid wooden construction elements can bend themselves into a defined shape without the use of external mechanical force.

According to a press release, the self-shaping process is based on the natural swelling and shrinking of wood caused by the moisture content of the material. When damp wood dries, it contracts more strongly perpendicular to the grain than along the grain. The researchers have taken advantage of this property by gluing two layers of wood together so that their grain directions are opposite to each other to form a ‘bilayer’ panel.

“As the water content of the bilayer panel decreases, one layer shrinks more than the other. Both layers are firmly glued together, so the wood bends,” said Markus Rüggeberg, who led the study. The researchers use a computer model to calculate the precise warping of the building component during drying, a process they call “wood programming”.

“Our approach enables a wide range of shapes and curvature radii. The concept of programming wood opens up new architectural possibilities for this regionally available, renewable construction material,” said lead author of the study Philippe Grönquist. Like Rüggenberg, he works at both ETH Zurich and Empa.

The 14-metre-tall Urbach Tower proves that the method is suitable for large-scale wooden constructions. It was built by architects and engineers from the University of Stuttgart together with the Swiss timber construction company Blumer-Lehman for the national horticultural show in Remstal near Stuttgart in May 2019.

Image credit: kindfolk via Unsplash

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