Effect of Incising and Preservative Treatment on Shear Strength of Nominal 2-Inch Lumber

Jeffrey J. Morrell, Rakesh Gupta, Jerrold E. Winandy, Djoko S. Riyanto


This study evaluated the effects of pretreatment incising of dry lumber and preservative treatment on the shear strength of 1980 pieces of 2 X 4 dimension lumber (nominal 50 mm X 100 mm X 3.6 m long). Three species groups (Douglas-fir, Hem-Fir, adn Spruce-Pine-Fir-South) and two commercially produced machine-stress-rated grades per species group were tested in torsion to determine their shear strength. Incising and preservative treatment produced significant reductions in the average shear strength of Douglas-fir, Hem-Fir, and Spruce-Pine-Fir-South dimension lumber. These effects need to be addressed through the development of more appropriate design values for uses of preservativetreated wood of these species when shear is a governing factor. An adjustment factor of 0.70 is proposed for incised and preservative-treated nominal 2-inch lumber.


Incising;preservative treatment;shear strength;MSR lumber;grade;torsion

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