Finite element analysis of vibrations on flexible structures due to turbulent wind
Notice bibliographique
Résumé
Wind load effects have a major impact on the design of numerous civil engineering structures. Building codes such as the National Building Code of Canada (NBC, 2015), the American Society of Civil Engineers Standards (ASCE-7, 2016) and the Eurocodes (Eurocode 8, 2016) display great details about the static effect of wind on different building shapes, surfaces and isolated exposed components. However, these standards provide very limited guidance on dynamic effects and current design methods are limited in scope and applicability, since they are based on dating experimental data such as a research from Vickery and Basu (1983), which did not use sophisticated experimental techniques as available nowadays. This research presents a dynamic analysis of two flexible telecommunication monopoles and a cantilevered sign structure, under static, harmonic and random wind loads using the nonlinear finite element analysis software ADINA. The analysis does not consider wind-structure dynamic interactions. The objective of this study is to investigate the response of different structures to a combination of wind actions and monitor any excessive or dangerous vibrations that may be engendered by resonance phenomena. Furthermore, the cyclic vibrations produced by wind can be used to assess the vulnerability of the modelled structures to fatigue and approximate their useful fatigue life. By modelling existing structures, field data can eventually be used to validate and adjust the models in order to mimic reality as much as possible and minimize uncertainty related to numerical predictions.After applying 100 random wind time histories to the three structures, it was first found that, for monopole structures, the suggested gust factor of 2.0 by CAN/CSA S37-18 is accurate in predicting the dynamic amplification produced by natural wind gusts, with maximum tip displacements values found to be amplified by 51% and 98% in comparison with the maximum equivalent static load. With further analysis of the critical case, the stress range was determined and compared to the fatigue limit of the material according to the S-N curve method (Wohler, 1855). It was found that the stress range would not exceed 50% of the value of the endurance limit of steel after 108 cycles of vibration for both monopoles. Thus, according to this method and under normal operating conditions, these two telecommunication towers will not likely suffer fatigue damages. Ambient Vibration Measurements (AVMs) were taken on one monopole and the first three modes of vibration of the structure as well as the damping corresponding to the first mode were obtained. It was found that the numerical model was about 10% stiffer than its real-life rendering. As such, the numerical model was adjusted beforehand to erase that disparity. The cantilevered sign structure was subjected to the same 100 random wind time histories and the maximum displacement observed at the end of the cantilever was 25 mm. This value corresponds to a 150% dynamic amplification from the maximum equivalent static load of 10 mm. CAN/CSA S6-18 proposes a gust factor value of 2.5 which corresponds to the exact amplification value found through dynamic numerical analysis. Once again, fatigue analysis showed results of stress range under 30% of the endurance limit of steel for this particular cantilevered sign structure after 108 cycles of vibration. Therefore, according to the S-N method (Wohler, 1855) and under normal operating conditions, this cantilevered sign structure will not likely suffer fatigue damages. Ambient Vibration Measurements (AVMs) were also taken on the sign structure and the first 4 modes of vibration of the structure were obtained. It was found that the numerical model was about 13% stiffer than its real-life rendering. Therefore, the numerical model was once again adjusted beforehand to correspond to the actual values measured in-situ
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 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 | 0,001 |
| 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 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,001 | 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 ».