Form and treatment effects on conical roundwood tested in bending

Summary This article presents the results and the comments of a sampling of 80 spruce conical roundwoods (tree trunks with the bark removed) of structural sizes tested in bending. Pressure impregnated samples were prepared with and without heart holes and paired with the untreated samples. Treatment effects have been studied in order to investigate their influences on the mechanical behavior. With a non-destructive evaluation by ultrasound, the mechanical results have been compared with an equivalent sawn timber series to analyze the effect of the form. The results show a negative influence of about 10% for the pressure-impregnated treatment on the mechanical properties only and up to 20% for the samples which were associated with pinholes for the heart treatment. On the other hand, the form effect increases the mechanical characteristics by 30% when compared to the square cross section. These results can be explained by a semi-ductile phase observed before failure. This conical roundwood form contributes to optimize the mechanical behavior linked to the anisotropic conditions where the grain is continuous and has a zero angle value with the longitudinal axis.