Low-frequency uniaxial stress reversal fatigue behavior of plain concrete
Bibliographic record
Abstract
This thesis investigates the uniaxial stress reversal fatigue behavior of plain concrete under low-frequency cyclic loading, with a focus on frequencies below 1 Hz. The research aims to enhance the understanding of the fatigue life of concrete structures, particularly in infrastructure subjected to repeated loading such as dams and bridges. The specimens were tested at three specific frequencies: 0.2 Hz, 0.5 Hz, and 0.75 Hz. These tests were performed under a constant stress range of 11.4 MPa, replicating the stress conditions identified through Finite Element Analysis of a spillway from an existing gravity dam in northern Manitoba. The testing regime set the maximum stress level at 90% of the tensile strength of the concrete and the minimum stress level at 20% of the compressive strength of the concrete. The analysis concentrated on evaluating the fatigue life of concrete, examining maximum strain curves, stiffness degradation, and energy dissipation under stress reversal conditions. The analysis revealed that higher frequencies generally resulted in a longer fatigue life. The maximum strain and stiffness degradation curves exhibited typical S-shaped patterns, indicating progressive damage accumulation in the concrete specimens, and increasing strain at failure. Additionally, stiffness degradation showed negligible differences in deterioration indices between 0.5 Hz and 0.75 Hz, with slightly higher deterioration observed at 0.2 Hz. Energy analysis indicated that higher frequencies result in increased energy dissipation per fatigue cycle. The application of the Weibull distribution effectively modeled the variability in fatigue life data, providing insights into the probabilistic nature of concrete's fatigue behavior under stress reversal loading. Furthermore, the research included a validation of the stress reversal fatigue model proposed by Ferreira et al. (2024). The model's applicability across different frequencies was assessed, demonstrating its potential for broader application in predicting the fatigue behavior of concrete under uniaxial stress reversal loading.
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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 | 0.001 | 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".