Characterization of Physical and Mechanical Properties of 2 by 4 Truss Lumber.
Forest Service research paper,
FOREST PRODUCTS LAB MADISON WI
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This paper summarizes data on dimensional characteristics, optimum grade, and regressions of strength on modulus of elasticity and grade class a function of strength ratio of lumber specimens sampled from truss fabricators in Illinois. Averages of dimensions, area, section modulus, and moment of inertia of the nominal 2- by 4-inch specimens at 12 percent moisture content were very close to those for standard dimensions 1.5 by 3.5 in. distributions of those properties tended to be skewed toward lower values. Mill grading of the lumber specimens was generally conservative compared to optimum grade levels based on the National Grading rule. Regressions of strength in compression, tension, or bending on an edgewise short-span modulus of elasticity appeared to be adequate for strength prediction or for machine stress rating. The two or three measures of bending strength at different positions in a specimen showed low correlation, suggesting that bending strength at one position in a specimen can be quite different from that at another position. This report, along with a previous report, provides a strength data base for engineering evaluation of wood truss reliability. The data on species, grade, and dimensions should be of interest to grading agencies and code groups. Author
- Wood, Paper and Related Forestry Products
- Construction Equipment, Materials and Supplies