Notice bibliographique
Résumé
Collapse of transmission towers can occur due to accidental loads such as conductor breakages, failures of insulators or other components, either under every day conditions (components with marginal strengths) or under extreme conditions such as ice storms, thunderstorms, tornadoes, fires, explosions, heavy mass impacts, etc. Furthermore, the trigger of one tower collapse may cause a catastrophic cascading failure of the whole transmission line section as was observed in the 1998 ice storm in Quebec, Canada. Knowledge of the post-elastic capacity of towers is necessary to mitigate the risk of cascading failures in overhead lines. The thesis presents a detailed study of the post-elastic response of latticed towers combining advanced (highly nonlinear) finite element analysis and full-scale dynamic testing of four tower section prototypes. The lattice towers are modeled with special three-node beam elements that include nonlinear material constitutive models for post-elastic response and the geometric stiffness matrices for elements are progressively updated to account for the second order effects. The numerical models also include the effects of connection eccentricities between diagonal members and the main leg members. The numerical models have been used to plan the physical tests and for re-analysis of the models with the experimental loads as measured during the physical tests. Four full-scale transmission tower model sections were built and tested under different load scenarios to verify the results from the numerical analysis. The salient conclusions of the research as follows: The research demonstrates that it is possible to use post-elastic analysis to accurately predict the reserve strength of bolted lattice towers provided connection eccentricities are properly modeled at peaks or cross arms loading points and in diagonals connected only on one leg. Both the numerical model and experimental results indicate significant post-elastic reserve strength of the tower section. In the tower prototypes tested in this research, the post-elastic reserve strength was 1.22 for flexure-torsion (i.e. tower under longitudinal loading) governed by diagonals, and 1.37 for bending (i.e. tower in transverse loading) governed by inelastic buckling of the main legs. Diagonal members affect the failure modes of transmission towers and their connection design may be a weak link in the development of their post-elastic capacity. Diagonal members connected on one leg only are subject to biaxial bending, they cannot develop the full strength of their cross section since the unconnected leg takes much less stress on its entire length. Accurate pushover post-elastic analysis is an essential design tool to ensure that the tower capacity is adequate and that failure modes are safe, i.e. not leading to progressive collapse. With appropriate training, such analysis is feasible in a design office. Observations from physical tests, confirmed by numerical simulations, suggest that failure modes under pushover static and dynamic pulse loading are similar. The ultimate loads sustained by the prototypes in the dynamic tests are higher than their static counterparts (162kN vs. 126kN in bending, and 57kN vs. 51.2kN in flexure-torsion); this can be explained by the strain rate effects, which were particularly large in the bending test due to a mass dropping height of 6 m.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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 | 0,000 | 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 tête enseignante, 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 ».