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Title: Bending creep and load duration of Douglas-fir 2 by 4s under constant load for up to 12-plus years

Author: Gerhards, Charles C.;

Date: 2000

Source: Wood and fiber science. Vol. 32, no. 4 (Oct. 2000).:p. [489]-501 : ill.

Publication Series: Miscellaneous Publication

Description: This paper finalizes research on graded Douglas-fir 2 by 4 beams subjected to constant bending loads of various levels and durations. Compared to results for testing in a controlled environment, results confirm that load duration did not appear to be shortened by tests in an uncontrolled environment, at least extending out to 12-plus years. By the same comparison, relative creep was considerably increased, however. The extended data also confirm that no evidence was found for a threshold below which stress levels for lumber can be maintained indefinitely. Based on the finalized prediction equations of this study and those of two previous studies, a factor of 2.0 for a 10-year load duration is more appropriate for Douglas-fir bending allowable properties than the 1.62 factor currently recommended. Also, bending deflections due to creep doubled sooner than commonly accepted. This research is important to structural engineers and code groups responsible for the safe design of wood structures when establishing new design criteria for load duration and deflection limits.

Keywords: Pseudotsuga menziesii, Lumber, Creep, Grading.

Publication Notes:

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

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Gerhards, Charles C. 2000. Bending creep and load duration of Douglas-fir 2 by 4s under constant load for up to 12-plus years. Wood and fiber science. Vol. 32, no. 4 (Oct. 2000).:p. [489]-501 : ill.

 


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