Analysis of the strength and stiffness properties for small diameter roundScots pine timber tested in bending and compression parallel to the grain

This paper is based on a study carried our: as part of a European Union (EU ) project titled Small Diameter Round Timber for Construction The project c omes under the EU's fourth framework programme (EU Fair Programme CT95-0091 ) and was initiated due to the fact that several EU countries have a surplu s of a small diameter thinning wood. The aim of the project is to develop s tructural systems in which thinning wood can be used in a round form and th ereby create new markers for dried, quality and strength classified small d iameter round wood. Subsequently, a supplementary study was carried out to look at the physical and mechanical properties of British and Finnish grown round Scots pine (Pinus sylvestris). The aim of the study is to fmd out if it is possible to use common strength grading rules for small diameter rou nd British and Finnish Scots pine. The hypothesis is that, independent of o rigin, the strength and stiffness of small diameter round Scots pine is con sidered the same, providing the specimens have the same physical properties . Strength and stiffness testing was performed in bending and compression p arallel to the grain. The standards EN 338 (1335), EN 384 (1335), EN 408 (1 995) and EN 518 (1995) have been used for the test procedure and determinat ion of the results. According to the multiple regression analysis, origin h ad no influence on the strength and stiffness properties of round Scots pin e. The manufacturing process was found to affect the strength properties. I t is clear that the more processed timber is weaker which is due the fact t hat processing breaks the outer wood fibers, and there is an increase in th e relative amount of knots. Most of the tested material belongs to a C30 st rength class. Finally, a visual strength classification criteria was establ ished for British and Finnish round Scots pine (Pinus sylvestris) to enable the selection of specimens for strength classes C24 and C30.