Progress Report on Survey of Bending Strength Values of Dimension Lumber Used in Farm Work Buildings in the Northeastern States

An attempt is being made to determine the range of strengths of ungraded northeastern lumber produced by small local mills and used in farm building construction. A study is underway to determine the practicality of developing simple rules that would either raise allowable strength values of this class of dimension material or insure specific performance. A field portion of the study has been a visual grading for bending strength of 2500 pieces of hemlock, spruce, white pine, and red oak 2 by 4’s and 2 by 8’s. The system involved using strength grades for knots, slopes of grain, shakes and splits, etc., previously developed. A machine testing of groups of pieces has shown that the field methods give adequate expressions of strength. The plan is to analyze the frequency distribution of the strength ratios for each species and size of lumber. Also, a compilation of the governing defects will be made. The frequency distributions of strength ratios can be applied to the known frequency distributions of clear wood strengths to give estimated actual strength values in the various lots of lumber. Consideration will then be given to suitable working stresses for such lumber when used for framing farm buildings.

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