Combined visual and machine strength grading

The aim of this study was to show the possibility of the classification of structural timber (European spruce) into strength class C35 according to EN 338 by using combined visual and machine strength grading techniques. Three different visual - machine strength grading combinations are devised for allocating sawn timber into strength class C35. They are composed on the one hand of the visual grading according to DIN 4074-1 and on the other hand of machine strength grading of green or dry sawn timber by measuring the dynamic MOE or the apparent density of sawn timber. In order to allocate sawn timber into strength class C35 the machine settings for these combinations were estimated. The grading results show that combinations based on the dynamic MOE are suitable for strength grading of lamellae for glued laminated timber and joists. Combinations based on apparent density are also suitable for strength grading lamellae for glued laminated timber.