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Official Journal of the Japan Wood Research Society

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Influence of knot area ratio on the bending strength of Canadian Douglas fir timber used in Japanese post and beam housing

Abstract

A study was conducted to establish the engineering properties and the influence of knot area ratio (KAR)-based grading rules on the bending strength properties of full-size Canadian Douglas fir timber used in Japanese post and beam building construction. In-grade tests were conducted on lumber selected at random from coastal mills in British Columbia, Canada, that manufacture products for the Japanese post and beam housing market. Bending strength and modulus of elasticity test results and KAR-based out-turn information on the 105 × 105 mm and 45 × 105 mm specimens are presented in this article. The in-grade test results indicate that KAR-based grading rules can be successfully applied to Canadian Douglas fir timber to meet strength property requirements.

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Correspondence to Shiro Nakajima.

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Lam, F., Barrett, J. & Nakajima, S. Influence of knot area ratio on the bending strength of Canadian Douglas fir timber used in Japanese post and beam housing. J Wood Sci 51, 18–25 (2005). https://doi.org/10.1007/s10086-003-0619-6

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Key words

  • Knot area ratio
  • Grading rules
  • Bending strength
  • Modulus of elasticity
  • Post and beam housing