The mechanical properties of wood are the most important when wood is used for constructional purposes. The influence of density and growth characteristics, comparing spruce and fir wood, on mechanical properties of constructions wood were studied. The elements with dimensions 38 x 100 mm, 50 x 150 mm, 44 x 200 mm, 140 x 140 mm with length 4000 mm were used in the study. Global modulus of elasticity (MOEg) and bending strength were determined at standard 4-point bending test. Growth characteristic were evaluated visually in accordance with SIST DIN 4074-1. We got the highest correlation coefficient when elements were placed in one statistical sample, e.g between wood density and MoEg (R = 0.74) and -0.61 between growth ring width and MOEg. The lowest correlation coefficient was achieved at relation between bending strength and distance of element from the pith (R = 0.09) and at correlation between compression wood share and MOEg of the tested elements (R = 0.09). Wood density and mean growth ring width were confirmed as the most reliable variables to predict mechanical properties of spruce and fir wood.
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