Behaviour of corbels reinforced with headed-end GFRP bars
Bibliographic record
Abstract
Steel-reinforced concrete (RC) corbels are commonly found in bridges, industrial buildings, and parking structures throughout North America. Corbels are structural elements with low shear span-to-depth ratio that transfer vertical and horizontal loads to other members such as columns or walls. Given that the vast majority of RC infrastructure in North America is aging rapidly due to steel corrosion, engineers face the challenge of designing replacement structures with innovative construction materials to meet or exceed the intended design life. Glass fibre-reinforced polymer (GFRP) bars have electromagnetically inert properties, which alleviate long-term durability concerns due to corrosion. Extensive research over the past two decades have proven that the use of GFRP bars in new structures is desirable to extend the service life. GFRP and steel have different mechanical properties; requiring separate design methods to ensure failure loads are accurately predicted and serviceability requirements are met. Headed-end bars enhance the anchorage achieved by GFRP under tie-action, helping minimize one of the key drawbacks compared to steel. Currently, Canadian building and bridge codes provide strut-and-tie modelling (STM) provisions to design steel-RC corbels, but the American code prohibits the use of this method for GFRP-RC corbels due to lack of research. This research program evaluates the use of GFRP headed-end bars as internal reinforcement for concrete corbel elements. Twelve (12) full-scale GFRP-RC corbels and two (2) steel-RC control specimens were constructed and tested to failure. The test parameters included main tie reinforcement ratio, secondary reinforcement ratio, shear span-to-depth ratio, and concrete strength. The parametric effect on serviceability criteria, strength capacity, and mode of failure were discussed. Performance of the experimental specimens were compared to available design provisions and analytical prediction models. The experimental results confirmed the formation of the STM through flexural and diagonal shear crack patterns. The thermoplastic headed-end bars used were found to be a viable anchorage method. The Canadian standards provided conservative shear capacity predictions for all evaluated corbels. The American code overestimated the shear capacity predictions for all evaluated corbels except one, suggesting that revisions are required to better predict the capacity of GFRP-RC corbels.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".