Rotational stiffness in timber joinery connections: Analytical and experimental characterizations of the Nuki joint

Abstract

Historic timber structures feature timber joinery connections that use interlocking geometries rather than fasteners. While timber construction since has gradually favored metallic fasteners, the longevity of historic timber structures utilizing joinery connections demonstrates their feasibility in structural systems and potential to enable sustainable constructions. Advancements in digital fabrication imply the ability to revitalize these complex geometries in competition with conventional fasteners. However, characterization of the mechanical behavior of joinery connections remains to be calibrated across analytical, experimental, and numerical models, let alone systematized across different geometric variations. This research examines the calibration between analytical models and experimental tests for the Nuki joint, a simple beam-through-mortised-column joinery connection. This paper shows that general elastoplastic behavior matches between models, and the analytical model can be calibrated to predict initial stiffnesses within 20% of those determined experimentally. Mismatches between models reveal challenges in calibrating across models: material irregularity of wood and fabrication tolerances.