Strength and Stiffness of Laminated Douglas-Fir Blocks in Perpendicular-To-Glueline Tension

Authors

  • Selwyn P. Fox

Keywords:

<i>Pseudotsuga menziesii</i>, glued-laminated beams, tension tests, pitched-tapered beams, size effects

Abstract

Blocks of commercial glued-laminated Douglas-fir were tested to failure in tension perpendicular-to-gluelines. The results of a two-level factorial experiment indicated that blocks 22 inches in length were weaker in strength than blocks 7 inches in length and that blocks of 5- X 5-inch cross section were weaker than blocks 3 X 3 inches. Additional longer specimens were tested to provide better estimates of their ultimate strength.

The average modulus of elasticity of 3- X 3-inch blocks was about 70,000 psi. Undetected ring shake caused early failure of some specimens, indicating that this natural characteristic might be responsible for unexplained failures of beams in service.

According to Weibull, specimen size affects material strength. To confirm application of his work to these tests, additional blocks of three other configurations were tested for strength. An assumption of a log-log relation as hypothesized by Weibull is acceptable. Test results of other researchers found from similar specimens show no noticeable deviation from the relationship.

References

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Published

2007-06-05

Issue

Number 2 / Summer 1974

Section

Research Contributions

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