Spricklast för dragbelastat trä med sektionsändring

Sammanfattning: On occasion, structural wooden members in tension feature a sectional alteration in the form of a notch. In spite of being a highly inhomogeneous and anisotropic material, as an approximation wood may be modelled as homogeneous and orthotropic. By means of such a material model, first order linear elastic theory and a fracture mechanics condition on the strain energy release rate, a formula is derived for the load bearing capacity with respect to fracturing. The capacity is further simulated in 2D with FEM both by employing a linear elastic method with node releasing and by a non-linear method with a cohesive zone. The validity of the analytical and numerical models are verified by laboratory tests comprising 21 small wooden members with varying notch size. The characteristic value of the capacity is determined by the 5th percentile with 75 % confidence level. The results show that the formula is successful in predicting the load bearing capacity of the wooden members which were tested. However, the size effect has yet to be established.