Parametric design and robotic fabrication of whole timber reciprocal structures

Abstract

To decrease the impact of the construction sector on climate change, sufficiently economic processes must urgently be developed to encourage the use of minorly transformed timber, such as tree trunks. However, the question remains how to inexpensively incorporate tree trunks with irregular morphology into structural systems from design to fabrication. It is only within recent years that robotic tools and parametric design software have made it possible to both quickly and affordably build with elements of geometry as variable as tree trunks. The objective of this article is to describe an automatic process, from parametric design to robotic fabrication, that makes it possible to build a full-scale structure from reshaped tree trunks. This research brings to light the scientific and technical challenges that must be undertaken before industrialization can be realized, therefore the geometric parametrization required of trunk-to-trunk connections is detailed herein. Finally, the authors describe a case study from design to fabrication of a full-scale 10 m × 5 m reciprocal structure prototype made from fourteen tree trunk elements fabricated as described above using robotic arms. It is seen that reciprocal structures can span large distances with logs of limited length, but their structural complexity brings additional challenges to the design and construction processes. This study highlights not only the need for future development to accelerate the processes of automatic scanning and cutting of timber logs, but also for mechanical characterization of logs using non-destructive methods and better prediction of transmission of stresses in wood-wood assemblies.