Mass Timber Joinery Design for Digital Fabrication and De-constructability

Abstract

Interest in sustainable architecture is pushing mass timber to the forefrontof the industry, but with it there are still difficulties in addressing topics such as the connections between elements. Traditional timber buildings utilized joinery to create a reversible connection between timber elements. By using modern fabrication and computational analysis we have developed a framework to rapidly prototype timber connections and develop modern design guidelines for mass timber joinery for both design and fabrication. Through generalization one can develop a system for timber joinery bybreaking the geometry down into simple parts. Using a geometric model for timber joints from a mesh derived from a NURBS geometry, we can determine metrics for any joint typology with information such as ’contact area’, ’overhang area’, and ’milling time’ from the interaction between the member faces. A finite element model allows us to make general assumptions about joint weakness by evaluating maximum stress and displacements. Using this data together, we can estimate a joint’s advantages in both fabrication and structure. Using this system, we were able to make a case study to test thesestrategies to see if design principles can be inferred from the analysis for a specific scenario. We used a scarf joint splicing two beams together as our metric for rapid prototyping. By creating a parametric model for the joint, we were able to quickly create both a simulated model and a physical model to compare benefits and limitations in the joint. These tools can be used for qualitative analysis between functionallyidentical joints and can produce metrics to compare each joint. These can help to inform design decisions with knowledge from disparate fields to develop designs that provide solutions for many issues.