Residual stress development of self-shaped wood bilayers for curved cross-laminated timber elements

Self-shaping of wood, an emerging technology, provides an innovative and sustainable means of manufacturing curved structural timber elements for construction. This technique harnesses the natural ability of wood to deform upon moisture changes in a predictable manner, without the need for extensive external shaping processes. Recent building projects successfully demonstrate the use of self-shaped wood bilayers as lamellae for load-bearing curved cross-laminated timber (CLT) elements. However, reliable information about the distribution and magnitude of residual stresses induced during self-shaping, as well as their implication on structural design, is still missing. This work employs advanced analytical and numerical modeling to investigate the complex mechanics of the wood bilayer shaping process, with a focus on the development of residual stresses in accelerated drying conditions. Results reveal that residual axial stresses in self-shaped lamellae may range close to design strength properties of structural timber, but remain below stress levels of conventional cold-bent curved lamellae. Residual rolling shear stresses were found to cause damage during self-shaping and to reduce expected curvature.