| Summary: | 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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