Wood heterogeneities and failure load of timber structural elements: a statistical approach

In this work, the effect of spatial location and geometrical characteristics of wood defects (only knots) on the failure load of timber structural elements is addressed. For a large set of timber structural elements (188 Maritime pine full size beams), spatial location and geometrical characteristics of knots were estimated from the analysis of external images of each element, and then, modulus of elasticity (MOE) and failure load obtained from a four-point bending test were experimentally estimated. From this large database, correlations between the failure load, MOE and geometrical characteristics of knots were studied on the basis of a polynomial regression and a nonlinear regression based on neural network. It was shown that accounting for simple geometrical characteristics of knots, such as the area, the circularity and the location, in addition to the MOE, significantly improves the prediction of the failure load of structural elements.