Bond and Development Length of GFRP Bars Embedded in Shotcrete
Bibliographic record
Abstract
Glass fiber–reinforced polymer (GFRP)–reinforced concrete structures can be efficiently constructed with the low cost and rapid concrete placement of sprayed concrete, termed shotcrete, whether for new construction or retrofit applications. This study is the first to investigate the bond strength and development length of ribbed and sand-coated GFRP rebar embedded in shotcrete using 20 notched beams. Two bar diameters (db) of 16 and 22 mm were tested with embedment lengths (le) of 20, 47, and 74 db. Four control beams were fabricated conventionally by pouring and vibrating the shotcrete mix, and 16 were shotcreted using the wet-mix process. Bond failure in 18 beams was by concrete cover splitting. Two shotcreted beams experienced pullout bond failures at significantly reduced bond strength as a result of large voids around the GFRP bars. Bond strength was, on average, 8% lower in shotcrete than poured concrete due to the presence of small voids in the shotcrete. For shotcrete beams without voids, the bond of shotcrete was equivalent to poured concrete. Ribbed rebar had, on average, a 21% lower bond strength than sand-coated bars. Overall, the bond of GFRP bars to shotcrete displayed similar trends as bond in poured concrete. Normalizing the embedment length with bar diameter (le/db) was found to inaccurately control for the effects of bar diameter and embedment length on bond strength. The bond equation in ACI CODE-440.11-22, overestimated the bond strength and did not accurately reflect the effect of concrete strength. This observation is most likely not limited specifically to shotcrete. A modified formulation of the ACI bond strength equation is presented that more accurately matches the observed trends of GFRP bond behavior, particularly the nonlinear variation of bar stress with le.
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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 | 0.001 |
| 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) | 0.001 | 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".