Contribution of Closed Ties to Shear Strength of GFRP-Reinforced Precast Concrete Tunnel Lining Segments: Experimental and Analytical Study
Bibliographic record
Abstract
Current tunnel design provisions do not consider the shear resistance of transverse reinforcement in precast concrete tunnel lining (PCTL) segments. Such reinforcement is often designed as a minimum for shrinkage and temperature resistance. This study evaluated the behavior and shear strength of PCTL segments reinforced with glass fiber‒reinforced polymer (GFRP) bars with and without closed shear ties. A total of five full-scale rhomboidal PCTL specimens with a 1,500 × 250 mm rectangular cross section and an arched length of 2,100 mm were constructed and tested under three-point loading up to failure. The testing parameters included the configuration of the transverse reinforcement (bars versus closed ties), the spacing of closed shear ties, the longitudinal reinforcement ratio, and concrete strength. The load–deflection behavior, cracking, failure mechanisms, shear capacities, and strain in the reinforcement and concrete are discussed herein. The results indicate that all specimens experienced shear failure because of the diagonal tension failure or shear compression mode. The presence of shear stirrups enhanced the structural performance of the GFRP-reinforced PCTL segments. In addition, increasing the closed-tie ratio, longitudinal reinforcement ratio, and concrete strength increased the shear strength of the segments. A comparison between the test results and predictions made with the critical shear crack theory (CSCT) was introduced in the theoretical approach to evaluate the applicability of existing FRP design code provisions. The predictions produced according to FRP design codes can be classified between conservative and nonconservative predictions. The modified CSCT yielded predictions closest to the experimental values with an accuracy of 98%.
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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 | 0.001 |
| 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".