Length effect of structural timber

Abstract: The purpose of this thesis is to evaluate the influence of the length effect of Structural timber. With that aim two samples with different length have been tested. Each sample has one hundred beams with the properties of both samples as close as possible. Engineering design methods for timber assume homogeneous material all along the beam, but in reality the strength is highly variable along a timber board. That fact implies that the real strength depends on length, load configuration, knots, MC and other factors. The failure of the beam occurs when the weakest seetian of the beam fails. The probability that a weak seetian is located within the beam increases with increasing length. First was found the weakest seetian for each board to be tested for bending strength. The grading system that was used is visual registration of knots. The Modulus of Elasticity, MOE, of each beam was found with a nondestructive test, then each beam was reloaded until failure. Two hundred boards of Norway Spruce, grown in Southern Sweden, were tested according to the European standard, EN 338 standard. The bending strength for two different lengths, 4 m and 2 m, were tested to see the influence of the length in bending strength. Both lengths were loaded with the same moment configuration of two-point load, but with different speed for the load applied.