Relationships between grade determining properties of Spanish scots and laricio pine structural timber

In a sample made up of 3312 boards of scots pine (pinus sylvestris) and 3318 boards of laricio pine (pinus nigra Var. Saltzmannii), both of Spanish provenance, and ranging in size from 100x40x2500 mm to 200x70x4500 mm, previously tested in accordance with the procedure set forth in UNE EN 408 standard, the relationships between the grade determining properties considered in the UNE EN 338 standard (bending strength, global and local modulus of elasticity in bending, density) are studied. In addition to these variables, the modulus of elasticity was also considered, calculated by means of the measuring of the transmission speed of an ultrasonic pulse generated by a Sylvatest device. The global modulus of elasticity calculated by measuring the deformation at the neutral axis seems to be the best predictor of the ultimate bending strength, while the local modulus of elasticity proves to be difficult to obtain, and has a lower predictive quality, and so its elimination is suggested. The need to consider one single testing procedure to determine the global modulus of elasticity is also analysed, along with the convenience of carrying out further studies regarding the use of ultrasonic techniques in order to predict the modulus of elasticity, due to the fact that the systems available are not sufficiently precise.