Climate and pest driven forest conversion is resulting in decreasing shares of coniferous species in Europe (e.g. BMLEH 2024). Modern wood-based construction heavily relies on softwoods, especially spruce (Picea abies). As a result, there is a need for alternative raw material sources including hardwoods. European beech (Fagus sylvatica), is a species with excellent mechanical properties in clear wood, relatively high tree growth rate, and widespread native populations over much of Europe. As the climate warms it may become more suitable in Scandinavia and the Baltic area (Kramer et al. 2010). It is especially interesting for structural use in service class 1 and can be used to make high performance glulam. For reasons of safety and resource efficiency, a reliable prediction of performance through grading is necessary for structural use. However, European hardwood species are notoriously challenging to strength grade due to lack of useful correlations (Kovryga 2023). One widely used factor in grading is density. While ring-width measurements are of doubtful power for visual grading density (Brunetti et al. 2020), a rule could be based on weighing (Ridley-Ellis et al. 2016). For machine grading, density measurement by weight or x-ray attenuation is quite common (Ridley-Ellis, 2025). However, as well as needing to correct for moisture content (not always easy to assess in production), the use of density as a grading indicator (for anything other than density itself) runs into the previously mentioned challenge of low correlations. This study investigates the significance of density for dynamic Modulus of Elasticity (MOEdyn) in beech. MOEdyn is a good estimator for tensile MOE (Ehrhart et al. 2016) and therefore useful for glulam grading. Density is needed as part of the measurement of MOEdyn, but how correlated is MOE with density?
Keywords: beech, density, dynamic stiffness, linear regression, disappointment
Authors
Simon Lux
Holzforschung Austria, Austria
Boku University, Austria
Dan Ridley-Ellis
Edinburgh Napier University, United Kingdom
Marlene Cramer
Edinburgh Napier University, United Kingdom
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