a pile of timber

Strength Grading of Timber

Timber exhibits large variations in mechanical properties, which makes grading of timber into appropriate strength classes important for the competitiveness towards other construction materials. Modelling and strength grading of timber has thus for more than ten years been an intense research area within the field of timber engineering and wood mechanics at Linnaeus University.

Our research

Timber is a naturally grown material that exhibits much larger variations in mechanical properties than what other common structural materials do. In order to utilize structural timber efficiently, it is therefore important to grade each piece into an appropriate strength class. The more accurate the grading, the more competitive structural timber becomes compared to other, less eco-friendly materials.

For more than ten years, modelling and strength grading of timber has been an intense research area within Wood Building Technology at Linnaeus University.

Models from detailed data

Accurate grading of structural timber is based on indicating properties (IPs) of strength, stiffness and density. IPs, in turn, are often based on comparatively inelaborate data from measurements, like axial resonance frequency, weight and dimensions of boards.

However, this is not sufficient for very accurate prediction of strength. Instead, detailed data from optical surface scanning, and/or data from X-ray scanning, should be collected and translated into models of individual timber boards. Using these, grade determining properties like strength can be predicted with higher accuracy.

Part of our research has already led to practical and accurate methods for machine strength grading. Other parts are more of basic research, expected to contribute to improved utilization of wood in a longer perspective. PhD theses presented by the group are Oscarsson (2014) and Hu (2018a).

Ongoing research comprise sub areas as follows.