Bending strength and stiffness of in-grade Douglas-fir and southern pine No. 2 2 × 4 lumber
Bibliographic record
Abstract
Douglas-fir ( Psuedotsuga menziesii (Mirb.) Franco) (DF) and southern pine ( Pinus spp.) (SP) trees are increasingly grown on intensively managed plantation forests that yield excellent growth. Lumber cut from these trees often contains a large percentage of juvenile wood, which negatively impacts its strength and stiffness. Design values of lumber must accurately reflect the available forest resource, and because the design values were determined over 25 years ago, questions exist whether wood quality has declined. To help address this, 1488 samples of commercial-grade No. 2 2 × 4 DF and SP lumber were destructively tested in edgewise bending. Mean stiffness of DF and SP was 11.51 and 10.89 GPa, respectively, comparing favorably with the 11.02 GPa mean design values; however, variation for SP was higher than in previous studies. The nonparametric 5th percentile bending strengths for DF and SP were 8.30 and 9.06 MPa, respectively. Both DF and SP tested at less than their design values, 9.3 and 10.34 MPa, respectively. Stiffness explained 66% and 52%, respectively, of the variability in strength for DF and SP. Because this relationship seems only moderately predictive, it may be prudent to couple stiffness with additional measures of quality when predicting bending strength.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".