Influence of cover on bond of strands prestressed by pretensioning
Bibliographic record
Abstract
Cover of prestressed tendons is an important factor that influences the transmission of prestress by bond. This paper describes a study of the influence of cover on the bond behaviour of prestressed pretensioned strands. Ten beams with different cover values were produced and tested. Bond at different levels of the percentage of transferring was studied. A second type of test was also performed to observe the behaviour of the beams when placed on two supports at the extremities and subjected to a point load at mid-span. Previous research works on bond of pretensioned tendons to concrete are presented in this paper. The experimental programme carried out at the University of Coimbra is described. Results from the tests are presented, analysed, and compared with Canadian, American, and European regulations. The results show that, in general, when the cover increases the transmission length decreases. A bilinear relationship between the transmission length and the cover is presented. The beams were placed simply supported and tested up to failure by means of a point load at mid-span. These tests showed that beams with a 20-mm cover withstood a load significantly lower than that predicted theoretically.Key words: prestress, bond, cover, concrete beams, prestressed structures, structural concrete.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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) | 0.003 | 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".