Strength grading of turkish black pine structural timber by visual evaluation and nondestructive testing
Keywords:Longitudinal vibration method, mechanical properties, Pinus nigra, stress wave method, visual strength grading
We examined the compatibility between the visual strength grading and the mechanical properties determined by using nondestructive and destructive test methods in Turkish Black Pine structural timbers. Fifty three structural timber were graded with three different visual strength grading standards; TS 1265, DIN 4074, and BS 4978. Dynamic modulus of elasticity was determined by longitudinal vibration (MOEdv) and stress wave (MOEds) test methods. The static modulus of elasticity (MOEs) and the modulus of rupture (MOR) of the timbers were determined in structural size in accordance with EN 408.
The average dynamic and static modulus of elasticity and modulus of rupture values of the timber sorted into best class of all standards were considerably higher than the lower classes. The differences in the modulus of elasticity values between the strength classes were found significant for British and German standards but insignificant for Turkish standard. However the decrease in modulus of rupture values with decreasing grading class was found significant for all standards. Best compliance between the visual grading class and the dynamic or static modulus of elasticity and modulus of rupture was observed for BS 4978. Strong correlations were found between the dynamic modulus of elasticity and static modulus of elasticity and modulus of rupture. Longitudinal vibration method showed better correlation with the static modulus of elasticity and modulus of rupture than stress wave method.
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