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UBC Theses and Dissertations

Structural property relationships for Canadian dimension lumber Liliefna, Leonard Dantje


Lumber property data from Canadian In-Grade Program for visually-graded dimension lumber are used to model lumber property relationships. The lumber properties studied are modulus of elasticity (MOE), modulus of rupture (MOR), ultimate tensile stress parallel to the grain (UTS), and ultimate compression stress parallel to the grain (UCS) for Douglas-fir, Hem-Fir and Spruce-Pine-Fir species groups. Structural property relationships based on three different approaches using Canadian dimension lumber have been modeled. The nonlinear models were adopted for the general stiffness-strength property relationships. The fitted regression models for the general stiffhess-strength property relationships then were used to model the strength property relationships. Band-width method was used to derive the relationships between modulus of elasticity and lower exclusion limits of strength values. The fitted models then were used to model the strength property relationships. The resulted models represent the relationship between two strength properties at the lower exclusion limit for lumber selected on the basis of modulus of elasticity. The strength property relationships derived using equal-rank method agree with that derived using general stiffness-strength property relationships. Therefore, for lumber selected on the basis of modulus of elasticity, the models derived using equal-rank method yield an average or mean trend for the estimated properties. The results of the analysis show that there exist good relationships between lumber strength properties. The strength property ratios for Canadian dimension lumber show significant species dependency particularly at the higher strength level. Property relationships trends are consistent across the species and methods of analyses. The property ratio models are intended to provide property estimates of characteristic values for untested properties. The property ratios for Canadian dimension lumber are significantly higher than that proposed by the American Society for Testing and Materials (ASTM) standard D 1990.

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