Wood is a versatile, but also complex construction material. Its properties vary due to many factors, such as species, the presence of knots or fibre orientation in the tree and subsequently in sawn timber, which makes the material behaviour difficult to predict (Swedish wood, 2025). Wood interacts with moisture from the surroundings causing dimensional changes, most dominantly tangentially along the growth rings. Cross laminated timber (CLT) possesses more consistent properties than sawn timber, due to the crosswise layering of boards, but in an outer layer, even small dimensional variations could accumulate and become noticeable in larger timber structures (Salzberger, Klein, Hemmerling, & Konstantinou, 2024). Individual boards in a layer have varying pith positions and thus growth ring curvatures depending on how they were sawn from a log. The growth ring pattern in a board influences the potential moisture induced dimensional change (Kettunen, 2006) (U. S. Department of agriculture, 2021) (Swedish wood, 2025) and the combination of boards with these variations in various constellations affects the mechanical properties of a CLT element (O’Ceallaigh, Sikora, & Harte, 2018) (Aicher & Dill-Langer, 2005). It is therefore likely that these combinations also have an impact on the dimensional stability of CLT due to moisture changes. To study the effects of such combinations on moisture induced dimensional changes, this project aims to develop a finite element model where the pith positions in single boards inside a CLT panel are varied using the Monte Carlo method, and where moisture induced changes are analysed in each variation.
Keywords: monte carlo simulation, cross laminated timber, moisture content, dimensional change, finite element method
Authors
Anna Eliasson
Wood Science & Engineering, Luleå University of Technology, Skellefteå, Sweden
Johannes A. J. Huber
Wood Science & Engineering, Luleå University of Technology, Skellefteå, Sweden
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