Computational design and digital fabrication of folded timber sandwich structures

This paper presents a detailed geometric design-to-fabrication procedure for a new type of timber sandwich structure that combines a folded assembly method and integral mechanical joints. The paper also investigates the hypothesis that such a combination creates a fast and highly-accurate assembly method for modular timber construction. A digital design procedure is first presented and includes a computational method to segment and unfold a target building profile and a computational method to digitally-fabricate segments as timber sandwich panels with integral press-fit and rotational press-fit (RPF) joints. Two structures were built to validate the procedure and hypothesised construction speed: a 30m(2) house comprising 6 identical folded timber arches, built in one week; and a 42m(2) canopy structure comprising 4 pairs of varying folded timber 'wings', built in two weeks. The as-built structures were 3D scanned and a defect analysis was conducted to assess the reliability and precision of assembled geometries. Both structures were highly accurate, with average absolute surface error generally less than the thickness of the timber material and an average angular defect for RPF joints generally less than 1 degree. In the few regions where larger surface error was observed, a strong correlation was seen with angular defect error and joint interlock failure in RPF joints at that location. Preliminary structural testing of the system also showed it to have a good load carrying capacity for its weight.