Mechanical Properties of Hybrid Softwood and Hardwood Cross-Laminated Timbers
Bibliographic record
Abstract
Cross Laminated Timber (CLT) is an engineered wood product consisting of an odd number (three to seven) of lumber layers, which are glued in an orientation of each layer perpendicular to other. After its introduction, CLT has been widely adopted in Europe since 1990s and has quickly become popular in the US in the last decade as a sustainable and cost-effective alternative to traditional building materials such as concrete and steel. The first version of PRG-320 was published in 2012 for the US and Canada to help designers and builders understand the properties of CLT and use it safely. The current version of PRG-320 only allows the use of softwood species for commercial production of cross-laminated timber (CLT) in the US. However, recent studies have investigated the possibility of using hardwood species for CLT and have shown promising results. In parallel to this, the next version of PRG-320 is being revised to include hardwood species. The inclusion of hardwood species is an effort to increase the value of underutilized wood species in the United States. This study presents the results from testing of three-layer and five-layer CLTs manufactured using yellow-poplar (Liriodendron tulipifera) as hardwood and southern pine (Pinus spp.) as softwood in different layers, defined as hybrid CLT. The purpose of this project was to compare the bending and shear properties in the major axis direction of hybrid CLT panels obtained from five-point, four-point, and three-point bending tests with the current ANSI/APA PRG-320 values, and also to evaluate their resistance to shear by compression loading and delamination according to ANSI A190.1 and AITC T110 standards, respectively. The bending strength and bending stiffness, except for some individual groups, as well as the shear strength and shear stiffness values exceeded the Grade V3 from PRG-320. However, the wood failure in resistance to shear by compression loading and face delamination in resistance to delamination were lower than the required values in the standards. The test results demonstrated that CLT groups consisting of yellow-poplar has strength and stiffness properties comparable to those consisting of southern pine. This suggests that yellow-poplar could be a promising alternative species to softwood in the production of CLTs.
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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 | 0.001 |
| 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) | 0.002 | 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".