Alberta Transportation Experience with Debonded Pre-Tensioning Strands in Precast NU Girders
Bibliographic record
Abstract
Precast concrete NU girders have been used in Alberta Transportation bridges since 2001 with spans ranging from 30 - 65m. These bridges consist of pre-tensioned NU girders which are typically post-tensioned in the field for longitudinal continuity. It is standard practice in Alberta to utilize deflected strands as well as debonded strands to minimize stresses at the ends of these girders during fabrication. The Canadian Highway Bridge Design Code (CHBDC S6-06) limits the number of debonded strands to a maximum of 25% of the total number of strands in the girder. Design engineers have found the code clause to be somewhat unclear and have often questioned whether the limits are applicable to girders which are pre-tensioned and posttensioned. In Alberta, it has been typical practice for designers to limit the percentage of debonded strands to between 25% and 40% of the total number of pre-tensioning strands in the girder and to stagger the strand debonding locations. On a recent project, NU girders were fabricated with over 50% debonded strands, all of which were debonded concurrently. This paper presents the engineering rationale that was developed to support the acceptance of these girders. For the covering abstract of this conference see record control number 201111RT334E.
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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 | 0.005 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.006 | 0.003 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.008 | 0.001 |
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".