Grading characteristics of structural Slovak spruce timber determined by ultrasonic and bending methods

The paper deals with evaluation of characteristics of structural Slovak spruce timber using an ultrasonic and a bending method. A destructive bending method was performed according to EN 408 and evaluated according EN 384. An ultrasonic device, Sylvatest-Duo, with build-in structural timber grading standards was used for measuring wave propagations velocity and gain of energy in wood. Result analysis showed differences in strength-modulus relations between the methods. Objectives results provided by the bending method give more reliable and real characteristics of MOEstat. Significant correlation between MOEstat and MORstat (r~0,7) was confirmed. Moreover, another strong correlation between MOR and wood density enhance reliability of the ultrasonic method. Strength and dynamic modulus characteristics from the ultrasonic method correspond to characteristic values of spruce timber according to EN 338, which can be consider as a simple and approximate grading method for structural timber. A part of the results can be used for determination of characteristic values of the Slovak spruce timber.