Integrating R-funicularity, local stability and inter-panel constraint assessment for discrete timber shell construction design

Timber shell structures are material efficient over large spans, and environmentally friendly due to the renewable nature of the material. In realising such structures, digital fabrication and assembly techniques provide new opportunities for the accurate conversion of complex digital designs into real components, allowing the generation of interlocking shell forms. Supporting falsework structures for shell construction present issues as a high waste factor in their assembly, due to their often single-use, and highly custom nature. Additionally, such segmented shells often rely on adhesives or additional fixings to constrain parts, reducing the potential for disassembly and reuse. This work presents a design approach, developed to demonstrate the use of dovetail style integral joints for maintaining structural stability through the assembly process, mitigating the need for falsework. The proposed approach is based on making use of stability assessments, funicularity measures and geometrical analysis of part interfaces to understand the behaviour of designed structures in an assembled state, during assembly, and how parts may be inserted into each other. Relaxed funicularity of full shell designs is quantified to assess fully assembled loading mechanisms, whereas the coupled rigid-block analysis (CRA) is used to assess the stability during assembly and is validated by comparison to physical models. Using the part-part interface geometry information and panel topology, inter-panel constraints are also assessed for both dovetail and finger joints. The developed interlocking joints are shown to aid funicularity by improving tensile capacity. Comparisons are made between inter-panel constraints and stability analysis data to show the relationship between interface geometry and stability. Together, these three techniques are shown to provide complementary early-stage design feedback to aid in generating feasible, discrete shell constructions.