SEISMIC RETROFIT OF REINFORCED CONCRETE FRAMES BY PROGRESSIVELY ENGAGING TENSION ONLY BRACES
Bibliographic record
Abstract
Non-ductile reinforced concrete frame buildings built prior to the enactment of modern seismic codes are often seismically deficient in terms of strength and ductility. Most of the conventional retrofit techniques, such as adding reinforced concrete shear walls or structural bracing systems, require intrusive construction practices, resulting in lengthy down times and expensive structural interventions. An alternative to conventional techniques can be use of high-strength prestressing strands or cables, diagonally placed as tension elements, either prestressed for increased building rigidity or non-prestressed tension elements. While the use of prestressing strands as tension bracing elements proves to be an effective technique, pinching of hysteresis loops associated with slack caused by yielding of the strands reduce potential energy dissipation capacity of the system. Furthermore, initial prestressing of the strands and the resulting stiffening effect on the frames lead to higher seismic forces, further reducing the effectiveness of the system. This paper aims to improve the previously observed deficiencies of the system, involving the use of progressively engaging prestressing strands. Accordingly, the strands are placed loosely as tension elements such that each strand engages in resisting lateral forces progressively when needed. The strands initially remain unstressed until the lateral drift becomes sufficiently high and the frame requires further lateral resistance. As the first strand yields and dissipates energy, the second and possibly the third stand starts engaging in lateral load resistances, while some strands remain elastic, recovering some of the inelastic deformations. Two tests have been conducted on existing concrete frames designed and built based on 1970 National B uilding Code of Canada, representing older construction practices. During the first test, the frame was retrofitted by one high strength strand while in the second test the frame was retrofitted by three strands, engaging in lateral force resistance at different stages. A numerical investigation of the concept was also conducted, using non-linear time history analysis of the frames, illustrating the performance of the cables.
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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 | 0.001 |
| 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) | 0.000 | 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".