Machine grading of Italian structural timber: preliminary results on different wood species

Italian forests are characterized by a high number of species, as a result of the great variability of climatic conditions, soil, altitude and exposure. Therefore there are many wooden species, potentially suitable for several uses, including structural. Currently, the structural timber used in Italy is mostly imported, partly because the technological characteristics of the national timber are little known. In the project supported by the EIM (Ente Italiano per la Montagna) and PAT (Provincia Autonoma di Trento), machine grading and bending tests were performed over 6 different wooden species (spruce, fir, Douglas fir, larch, Corsican pine, chestnut). About 1,600 rectangular cross section beams (2 different cross section sizes per species) have been evaluated with a grading machine that combines the determination of dynamic modulus of elasticity with X-ray imaging analysis (GoldenEye-706), and then tested in the laboratory according to EN 408. The results show first of all the good mechanical performances of some Italian wooden species, in particular Douglas fir and pine. The dynamic modulus of elasticity was generally well correlated with the values determined by bending test. Moreover, the efficiency of the grading, determined according to the optimum grade as required by EN 14081-2, was variable depending on the species, and therefore its specific wood properties. Although the number of specimens analyzed is not large enough to validate a procedure for initial type testing, the results obtained are interesting from the perspective of the Italian timber promotion.