Grades standardize the quality of lumber at different levels and are based on moisture content, size and manufacture at the time of grading, shipping and unloading by the buyer. A summary of the six published design values?including bending (Fb), shear parallel to grain (Fv), compression perpendicular to grain (Fc-perp), compression parallel to grain (Fc), tension parallel to grain (Ft), and modulus of elasticity (E and Emin) can be found in Structural Properties and Performance published by WoodWorks.Ĭanada has grading rules that maintain a standard among mills manufacturing similar woods to assure customers of uniform quality. Design Values for Wood Construction, which is a supplement to the ANSI/AF&PA National Design Specification? for Wood Construction, provides these lumber design values, which are recognized by the model building codes. The applicable standards are based on results of tests conducted in cooperation with the USDA Forest Products Laboratory. Current standards are set by the American Lumber Standard Committee, appointed by the Secretary of Commerce.ĭesign values for most species and grades of visually graded structural products are determined in accordance with ASTM standards, which consider the effect of strength reducing characteristics, load duration, safety and other influencing factors. These standards have changed over the years to meet the changing needs of manufacturers and distributors, with the goal of keeping lumber competitive with other construction products. The move to set national standards for lumber in the United States began with publication of the American Lumber Standard in 1924, which set specifications for lumber dimensions, grade, and moisture content it also developed inspection and accreditation programs.
Therefore, they vary considerably in strength, utility and value. Individual pieces of lumber exhibit a wide range in quality and appearance with respect to knots, slope of grain, shakes and other natural characteristics. Structural Wood Lumber Engineering Properties | Modulus of Elasticity of Wood | Wood Engineering Design Data.Structural Wood Lumber Engineering Properties 5" and Larger
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