Prediction of bending strength in oak beams on the basis of elasticity, density, and wood defects

Abstract

The purpose of the study was to propose accurate models for predicting bending strength that are valid for a wide range of beam qualities. For the study, 26 European oaks (Quercus robur L.) were felled in northwestern Spain, where most of the oak stands in the country are located. The trees were sawn, and a sample of quartersawn planks was selected. Planed and edged specimens (5×10×200 cm) were tested to obtain the modulus of rupture (MOR) in axial direction bending, the modulus of elasticity (MOE), density, moisture content, and size of defects. The MOR was correlated with the MOE and with maximum edge knot diameter. The correlation was not high enough to justify construction of a predictive model of mechanical behavior on the basis of maximum knot size in the piece. The analyses enabled development of a model for predicting MOR, with MOE as the only predictor variable (R 2=0.65; bias=0.6%)