Assessment and evaluation of corrosion on response of girders of Champlain bridge
Bibliographic record
Abstract
The old Champlain Bridge provided an important transportation corridor for Montreal, connecting the south shore of the St. Lawrence River to the island of Montreal. The bridge was opened in 1962 and demonstrated signs of distress as early as the 1980s and 1990s. Once the new Samuel de Champlain bridge was opened in 2019, the deconstruction of the old Champlain bridge gave researchers the opportunity to study the actual state of corrosion within the post- tensioned girders and the subsequent impact on the capacity of the girders under shear and moment. This thesis presents the results of these findings. Large 3m high by 5m long segments of the girders from section 5 and section 7 were taken to a storage site where samples could be taken from the specimens. Carbonation tests were performed and samples of concrete throughout the depth of the member were taken, enabling chloride concentration profiles to be determined. The results of these tests showed that chlorides did not penetrate deep enough to reach the prestressed tendons from the surface of the girders. This evidence, together with reflective cracking along the tendon profiles indicated that the water containing deicing chemicals likely entered the post-tensioned ducts at the tendon anchorages. Visual inspection enabled the degree of corrosion of the tendons to be evaluated. The impact of the tendon loss due to different degrees of corrosion on the moment and shear capacity of the girder was predicted using Response 2000. Edge girder P7 of span 28W-29W in section 5 showed the highest level of corrosion, with as many as 19 out of 24 post-tensioned tendons lost to corrosion. In 2014, only half of the tendons were predicted to have been lost, at which point the factored flexural resistance was calculated to be equal to the service moment at midspan and hence, failure could have occurred at service level loading of the bridge, if all girders in the span experienced the same degree of corrosion. The seven girders in a typical span actually experienced different degrees of corrosion, with the edge girders experiencing greater corrosion, however strengthening measures were required. Edge girders P1 and P7 of span 12E-13E in section 7 were shown to be in better condition, with no significant corrosion found in the tendons and only minor reflective cracking. This study gives insight as to the importance of monitoring tendon corrosion in post-tensioned structures, and that care needs to be taken when estimating the number of corroded tendons based on visual inspections. It is noted that the actual bridge had undergone various strengthening measures to ensure the safety of the bridge until the new bridge was constructed
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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 | 0.000 |
| 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".