Predicting The Effect of Moisture Content On The Flexural Properties of Douglas-Fir Dimension Lumber

Authors

  • David W. Green
  • James W. Evans
  • J. David Barrett
  • E. Nicholas Aplin

Keywords:

Flexural properties, modulus of rupture, modulus of elasticity, flexural stiffness, moment capacity, moisture content, mathematical models

Abstract

Current procedures for adjusting estimates of the mechanical properties of lumber for changes in moisture content are based on trends in the observed means. The present study was initiated to develop analytical procedures for adjusting estimates of the flexural properties of 2-inch-thick Douglas-fir dimension lumber that would be applicable to all levels of the flexural properties. Equations are derived for adjusting modulus of rupture (MOR), modulus of elasticity (MOE), moment capacity (RS = MOR x section modulus), and flexural stiffness (EI = MOEX moment of inertia) for changes in moisture content. The best of these equations are found to be significantly more accurate than current procedures for adjusting estimates of strength properties such as MOR and RS. Because MOE and EI are less affected by changes in moisture content, most of the equations work well for these properties.

References

American Society For Testing and Materials. 1986. Establishing structural grades and related allowable properties for visually graded lumber. ASTM D 245-81. Philadelphia, PA.nAplin, N. E., D. W. Green, J. W. Evans, and J. D. Barrett. 1986. Moisture content and the flexural properties of Douglas fir dimension lumber. USDA Forest Serv., Res. Pap. FPL 475. Forest Prod. Lab., Madison, WI. 32 pp.nForintek Canada Corporation. 1983. In-grade testing program maintains U.S. compatibility. The Forintek Review 1(2):3-4.nGerhards, C. C. 1968. Four-inch southern pine lumber: Seasoning factors for modulus of elasticity and modulus of rupture. Forest Prod. J. 18(11):27-35.nGerhards, C. C. 1970. Further report on seasoning factors for modulus of elasticity and modulus of rupture. Forest Prod. J. 20(5):40-44.nGreen, D. W. 1982. Adjusting the static strength of lumber for changes in moisture content. Proceedings, Workshop on How the Environment Affects Lumber Design: Assessments and Recommendations. Forest Prod. Lab., Madison, WI, 28-30 May 1980. Pp. 86-105.nGreen, D. W. 1983. In-grade testing impetus for change in the utilization of structural lumber. Proc. Conf., From Stump Through Mill: Recent Advances in Spruce-Fir Utilization Technology. Univ. of Maine at Orono, 17-19 August 1983.nGreen, D. W., C. L. Link, A. L. Debonis, and T. E. Mclain. 1986. Predicting the effect of moisture content on the flexural properties of southern pine dimension lumber. Wood Fiber Sci. 18(1): 134-156.nMadsen, B. 1975. Moisture content-strength relationship for lumber subjected to bending. Can. J. Civil Eng. 2(4):466-473.nMadsen, B. 1982. Recommended moisture adjustment factors for lumber stresses. Can. J. Civil Eng. 9(4):602-610.nMadsen, B., W. Jansen, and J. Zwaagstra. 1980. Moisture effects in lumber. Structural Research Series, Rep. No. 27. Dep. Civil Eng., University of British Columbia, Vancouver.nMclain, T. E., A. L. Debonis, D. W. Green, F. J. Wilson, and C. L. Link. 1984. The influence of moisture content on the flexural properties of southern pine dimension lumber. USDA Forest Serv. Res. Pap. FPL 447. Forest Prod. Lab., Madison, WI.nU.S. Department of Agriculture. 1974. Wood handbook: Wood as an engineering material. USDA Forest Serv., Forest Prod. Lab., Madison, WI. 40 pp.nU.S. Department of Commerce. 1986. American softwood lumber standard. Voluntary Product Standard. PS 20-70 National Bureau of Standards.nWilson, T. R. C. 1932. Strength-moisture relations for wood. U.S. Forest Serv. Tech. Bull. No. 282. Forest Prod. Lab., Madison, WI.n

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Published

2007-06-22

Issue

Number 1 / January 1988

Section

Research Contributions

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