Geodesic beam networks

In the design of material efficient structures the relation between form and force play a very important role. Gridshells, compression vaults and tensile surface structures are examples that clearly show how curvature and form can considerably reduce material usage by carrying the loads through geometry and not through mass. Furthermore, wood can be the sustainable and environmentally friendly building material that we need, since it’s a naturally growing organism and can thus provide an infinite and thus sustainable material resource, when maintained properly. Hence, intelligently designed curved timber systems can be a part of the solution to the problems the building sector is facing. However, fabricating curved timber elements proves to be a difficult and wasteful task, which often requires extensive molding and machinery, pressing and gluing. Recently, the study of bending-active structures has led to new manufacturing approaches in which curvature is generated by elastically bending initially flat elements into a desired shape. However, the scaling of these systems has been shown to have structural limitations, and are therefore rarely seen in large-scale architectural applications, rather confining their realization to demonstrator-size prototypes. These limitations can be overcome by stacking multiple individually bent lamellas and coupling them together. Chemical lamination of the individual lamellas underlies the construction principle of glued laminated timber, and engineered wooden products (EWP). Although providing a structurally efficient bond, the usage of such synthetic adhesives compromises the sustainability and recyclability of the product. Synthetic adhesives are produced from oil and gas, which is known to be responsible for vast amounts of Greenhouse Gas emissions and furthermore they are directly harmful to the environment due to the emission of toxic gasses (Sotayo, 2020). To improve the environmental performance of EWPs, adhesive-free timber products are being researched and developed. In the 1990’s the research laboratory IBOIS at EPFL in Lausanne Switzerland led by Prof. Julius Natterer developed the ribbed timber shell, which is an adhesive-free mechanically laminated timber system. The system is constructed by stacking continuous wooden planks in crossing directions and filling the gaps in between the planks with shorter pieces, so-called infill layers, and finally screwing the package together, to form a material efficient structural system suited for large-scale applications (Figure 1).

This project aims to continue to develop and validate the previously developed analysis approaches. But it will mostly focus on system developments and exploring the geometrical and constructive boundaries and how those can be overcome by means of computational modeling and digital fabrication.

The strategy of cutting every other layer into smaller infill pieces that has been applied so far is a low-tech and pragmatic approach that facilitates the production and construction. However the design of the structure gets confined by the infill with the highest curvature to length-ratio, since the elastic bending energy is proportional to the length and the curvature of the element.

To overcome these restrictions, we will investigate how strategic scoring or milling can reduce the elastic energy and bending stresses in the lamellas. We will elaborate on these principles by developing, studying and validating strategies to achieve a broader range of currently unexplored structural geometries. This will aid at broadening the scope of mechanically laminated timber beam networks and will thus significantly increase its application potential in large-scale architectural and structural design.