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    A sampling of nominal 6- by 8-inch (standard 140- by 184-mm) Douglas-fir timbers was obtained from an industrial military building in Minnesota. Thirty selected timbers had heart checks (boxed heart splits), which are characteristic of most old timbers installed in dry locations. Sixty selected timbers did not have heart checks. Most of the beams would grade as Select Structural Beams and Stringers by current grading rules. The modulus of elasticity (MOE) of the unchecked beams was greater than the allowable values given in the National Design Specification, but the modulus of rupture (MOR) was low. Analyses of the results suggested that heart checks decrease the mean MOR about 15 percent but have no direct effect on MOE. A good correlation was found between MOE determined by longitudinal stress wave techniques and that determined in static edgewise bending. Results suggest that the feasibility of developing mechanical grading systems for reclaimed timbers might be useful for on-site grading. Additional data are needed on wider beams with heart checks than those used in this study to confirm this hypothesis.

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    Green, David W.; Falk, Robert H.; Lantz, Scott F. 2001. Effect of heart checks on flexural properties of reclaimed 6 by 8 Douglas-fir timbers. Forest products journal. Vol. 51, nos. 7/8 (July/Aug. 2001).:p. 82-88.


    Pseudotsuga menziesii, Building timbers, Checks, Wood defects, Flexibility, Modulus of elasticity, Beams, Bending, Minnesota

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