Simulation of wood deformation processes in drying and other types of environmental loading*

Deformation processes in wood exposed to drying and other types of environmental loading are simulated by use of the finite element method. In the material model applied, the orthotropic structure of the wood material is considered. The differences of properties in the longitudinal, radial and tangential directions for stiffness parameters as well as for moisture shrinkage parameters are taken into account. As an illustration of possible application areas, the deformation development of boards during drying is simulated. In the analyses, the influence of spiral grain and the variation of wood properties with the distance from the pith are considered. The simulation yields information about unfavourable deformations that develop during the drying process.Simulation du processus de déformation du bois par séchage et autres types de charges environnementales. Le processus de déformation du bois exposé au séchage et autres types de charges environnementales est simulé par la méthode des éléments finis. La structure orthotropique du bois est prise en considération sur le modèle de matériel utilisé. Les différences existant au niveau des propriétés des directions longitudinales, radiales et tangentielles sont prises en compte pour les paramètres de rigidité et de contraction par humidité. Une des possibilités du champ d'applications est illustrée par le fait que l'évolution de la déformation des planches pendant le séchage est simulée. À l'échelon des analyses, l'influence du grain spiral et la variation des propriétés du bois avec la distance depuis la moelle sont pris en compte. La simulation permet d'obtenir des informations concernant l'évolution des déformations défavorables pendant le processus de séchage

Finite Element Simulation of Mechanical and Moisture-Related Stresses in Laterally Loaded Multi-Dowel Timber Connections

Numerical simulations of stress distribution within a moment stiff timber frame corner have been performed. The frame corner is a multi-dowel connection with two slotted-in steel plates. The interaction between the fasteners and the wood material is modelled as a full contact interaction based on penalty formulation. The wood material is assumed to be an orthotropic material in reference to elastic and shrinkage behaviours. Both mechanical loading (from snow and wind) and moisture loading have been studied. Model adaptivity was used to reduce the computer time and to find suitable coupling conditions between beam and solid elements. The simulation results have been compared with typical hand calculations. The conclusion is that the hand calculations diverge quite a lot from the simulation results and relatively small moisture changes can cause significant stresses in areas adjoining the fasteners