A parametric investigation of the influence of knots on the flexural behaviour of wood beams

The presence of knots significantly influences the mechanical behaviour of timber. This research presents a parametric finite element analysis of the effect of knot characteristics on the flexural capacity of wood beams. Parameters include knot radius, longitudinal and vertical positions, length, and diving angle. The generation of the FE model is based on a technique developed in a previous research stage, and bending tests on a set of beams were employed for the validation. The numerical model accurately recreates the three-dimensional geometry of the knot and related fibre deviations. The capacity of the beams under bending is evaluated via the Tsai--Wu failure criterion. Findings reveal that the presence of knots in the tension zone leads to an early tensile failure and insufficient utilization of compression capacity. The decrease of bending capacity may rise to 39\%, and the knot inclination may positively or negatively influence the behaviour depending on the diving angle.