Modelling Workflow for Segmented Timber Shells Using Wood-Wood Connections

Abstract

This paper presents a modelling method based on planarization for double-curved segmented timber shell made from quad polygons and assembled by wood-wood connections. The inspiration is taken from timber dome structures [1, 2], where solid timber walls were built from planks, connected side by side. Furthermore, the research is based on a collaboration with a local timber company located in a mountain area. In this context, timber has a low economic value because the price no longer covers the harvesting costs [3]. Therefore, there is a need to explore the available timber stock (round wood, beam elements and planks) to transform it locally. The geometry modelling workflow is split into three parts: surface discretization, joint modelling and fabrication. Firstly, projection-based solver is applied to the planarization of volumetric blocks. Secondly, the joint geometry is computed according to the insertion vector and a tool-path is generated using G-Code [4] to guide the 4.5 Axis CNC machining. As proof of concept, two prototypes were built, one from planks and another from round-woods. The choice of material influenced the segmentation of the timber shell. Finger and Tenon-mortise joinery techniques have been chosen for their simple modelization and fast cutting time. Their placement follows as closely as possible fiber orientation of wood. Even if both study cases share the same discretization method, the first prototype from timber plates takes advantage of lightweight structures, while the second explores a heavy solid round-wood structural system.