Structural performance of precast concrete tunnel lining segments reinforced with GFRP bars under bending load
Bibliographic record
Abstract
Abstract: In underground tunnels made using tunnel boring machine (TBM), the lining is constituted of precast concrete tunnel linings (PCTL) segments. Such PCTL are subjected to corrosive environment especially where they are exposed to wastewater or aggressive soil. Rehabilitation or renovation of corroded reinforced concrete (RC) tunnel segments is accompanied by problems such as very high cost, difficulty and serviceability interruption. An alternative approach to deal with corrosion problem in conventional RC tunnel segments is the use of glass fiber-reinforced polymer (GFRP) bars as a substitution of conventional steel reinforcement. Application of GFRP bars in tunnel segments requires a comprehensive research program for experimental, and analytical investigation of GFRP-reinforced PCTL segments. In this project, novel PCTL segments were tested under three-point bending load. Different parameters of longitudinal reinforcement ratio, size and spacing, configuration of transverse reinforcement (closed stirrups and U-shape stirrups) and type of concrete (normal-strength, high-strength and fiber-reinforced concretes) were considered in the experimental program. In order to achieve the objectives of the experimental phase, a total of 12 full-scale tunnel segments were tested. The segments had parallelogram shape with the arc length of 3100 mm, width of 1500 mm and thickness of 250 mm. The experimental results were evaluated through cracking behavior, failure mechanism, load carrying capacity, serviceability, load-deflection behavior, strain analysis, ductility, and deformability. The experimental program was followed by analytical investigation to evaluate existing models and propose new models to predict flexural strength, shear strength, crack width, deflection and interaction diagrams. In addition, newly developed models were provided to consider the effect of curvilinear shape of a segment on its flexural and shear strength. According to the test results, GFRP-reinforced PCTL segments showed satisfactory failure mechanism, cracking behavior, deflection behavior, and deformability. The structural performance can be further improved by using high strength concrete and fiber-reinforced concrete. Increasing the reinforcement ratio improved the post-cracking stiffness, cracking behavior, flexural strength, and shear strength while changing the mode in some cases. The overall structural performance of GFRP-reinforced PCTL segments with closed ties and U-shaped ties was similar. Finally, the developed analytical models showed a good agreement with the experimental results.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".