Wood is derived from living trees and therefore, changes its shape depending upon its moisture content. It contracts upon drying, and researchers are trying to make use of this contraction for creating curved structures without having to rely on machines. The simulations and the resulting test structure have been described in a new paper.
A number of techniques exist that can be used for curving the wood by hand. Curved wooden pieces can be created by making use of bandsaw, clamps, and glue, or by heating the timber to a temperature of 99 degrees Celsius. However, mass-producing curved wood is an inefficient process that ends up leaving an appreciable amount of waste. Machines that are used for curving the wood will simply grind or cut the parts off that are not required.
Of course, it gets the job done. But, the waste is too much. That is where scientists from the Laboratory for Cellulose & Wood Materials, the Institute for Building Materials (EMPA), ETH Zurich in Switzerland, and the University of Stuttgart (Germany) have come up with a new method that allows them to bend the wood itself into a pre-set shape. This is achieved without making use of any kind of mechanical force.
When a piece of damp wood loses its water content, it will begin to contract perpendicular to the grain. This means that it creates a 90-degree angle to the grain. This is an undesired effect since it generally causes wood warping. However, the team of scientists was able to utilize the warping process in a way that benefited them. What did they do? They glued two layers of wood together, thus creating a bilayer panel. A bilayer panel is defined as an assembly of wood where the grain directions are opposed to one another.
When the water content of the bilayer panel is decreased, one layer shrinks more as opposed to the other. Markus Rüggeberg explains, ‘Both layers are firmly glued together, so the wood bends.’ Markus is affiliated with EMPA and ETH. He led the study as well. The scientists have termed their technique as ‘wood programming.’ They rely on the thickness of the layers, grain direction, and the moisture content of the wood for creating a computer model that helps them to calculate the precise warpage of the building component while it dries.
Once the bilayer panel has attained its goal, it can be glued together to other bilayer panels. This is a process known as lamination. Laminated wood is a common sight, and it is utilized for keeping the structure stable even when the temperature is changing. Philippe Grönquist is the lead author of the study and said, ‘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.’
The structure built by the team has been named as Urbach Tower. It is located in the small town of Urbach in Germany. It is a 45-foot tower that has been designed for the sake of providing ‘a place of shelter, internal reflection, and outward view by revealing stunning vistas and framing the landscape.’