Timber structures made of naturally curved oak wood: prototypes and processes

Abstract

Highly optimised processing workflows characterise today’s wood industry. The gained efficiency is mainly directed towards making standardised linear materials that fulfil the market’s expectation of a continuous flow of identical products with certain constant specifications. The research presented here seeks to question these limitations and provide another approach to the use of wood in construction. The study involves complex geometry handling, architectural design, and material and structural considerations. Trees absorb CO2 during growth, and as a construction material, wood can function as CO2 storage, thereby reducing the levels in the atmosphere during the lifetime of the building—and even longer if the building components can be reused. We have seen a significant rise in wood construction over the past few years. This is partly due to growing climate awareness and the increased availability of engineered wood products (EWP). EWPs are reliant on uniform tree production. With growing interest in using wood for construction, an increase in plantation forests is predicted, leading to a lack of biodiversity in the affected areas. The consideration for the general climate expressed through the increased use of wood as a building material may thus appear to be in contrast to the efforts to improve biodiversity. This research seeks to provide an alternative route where non-uniform wood, usually used as firewood, can be used as a construction material. The project demonstrates possibilities that emerge from engaging with the wood as a specific occurrence of a biological entity rather than a standardised material. While historical precedents inspire the research, the project has been developed using digital tools, such as laser scanning, algorithmic design and robotic fabrication. We have developed a unique design-to-production workflow that uses curved natural wood in its original form to enable curved architectural designs. The workflow thereby links the inherent properties of the wood to a distinct mode of expression. The wood is retrieved from a sawmill that collects discarded tree trunks from local forests. The sawlogs are registered with a 3D scanner, and a customised parametric method is used to handle the geometric information and establish a database of the irregular saw logs. A custom-made algorithmic design tool identifies where the sawlogs fit best in a predefined construction design based on the database. Machining data is directly extracted for the subsequent robotic processing. The irregular shape of the material suggests a discrete analysis of the structural properties of each component. A series of destructive physical tests are carried out to indicate the capacity of the structural system and the joint solution. To demonstrate the viability of the workflow, study challenges in controlling tolerances and humidity, and develop an assembly strategy, we have produced a construction prototype of 15 members in the size of 3 m in width and 4 m in height.