ABSTRACT
Wood is an anisotropic material, i.e. its mechanical properties depend on the considered direction, and its mechanical behaviour is strongly affected by the complex material anatomy. In fact, wood is a natural biological material designed to resist loads (gravity, wind, inclination of terrains and others), by means of an internal structure that maximise strength and stiffness in stressed directions. Actually, wood cells are oblong and predominantly oriented in the grain direction, giving rise to a strong direction along the longitudinal axis of the trunk, while in the other two directions stiffness and strength are remarkably inferior. Accordingly, from a macroscopic point of view commonly assumed for structural design purposes, wood is generally considered as a cylindrical orthotropic material, with the principal axes of orthotropy (L, R, T) given by the longitudinal or grain direction of the tree trunk, radial and tangential directions (Figure 2.1).
