Strength of European timber: Part 1. Analysis of growth areas based on existing test results

Joint analysis of existing strength data for major commercial European timber species is presented in this report. The work has been carried out as a co-operative venture between 6 research institutes from 6 countries. The main objective of the work was the analysis of growth area issue for European grading standard: in which regions common grading machines settings can be used. This research is mainly based on laboratory measurements of grade indicating properties: static and dynamic modulus of elasticity, knot area ratio (KAR), density, tension and bending strength. Results for thousands of test specimens from Central and Northern Europe are analyzed. The results indicate that it is reasonable to determine different settings for Central and Northern Europe. In the case of grading spruce for glued laminated timber where tension strength is determined, differences between Central and Northern Europe are small and it may be possible and economically feasible to use the same settings for a large area when advanced grading methods based on measurement of stiffness and knot size related properties are used. When grading Scots pine for bending properties it is obvious that different settings are needed for Germany, France and UK, whereas the Nordic countries may use the same settings. After the analysis of existing data the project continues with a new experimental programme after which more definitive conclusions can be expected.