Assessment and evaluation of corrosion on response of girders of Champlain bridge
Notice bibliographique
Résumé
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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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».