Seismic Performance Evaluation of Steel Buckling-Restrained Braces Subjected to Subduction Interface Earthquake Demands
Notice bibliographique
Résumé
Steel Buckling-Restrained Braced Frames (BRBFs) are commonly used as lateral-force resisting systems in multi-storey buildings located in high seismic regions of North America. The reliable seismic performance of BRBFs is attributed to their Buckling-Restrained Braces (BRBs), which provide high ductility and energy dissipation capabilities. BRBs were first developed in Japan in 1988, later adopted into the AISC Seismic Provisions (AISC 341) in 2005, and subsequently incorporated into the Canadian steel design standard (CSA S16) in 2009. Canadian standards have since referenced the BRB prequalification provisions from AISC 341, which require two tests: (1) a uniaxial test to evaluate the performance of the device, and (2) a subassemblage test to assess stability under additional rotational demands introduced by the connections. Both tests must be conducted under a standardized symmetrically increasing loading protocol, which was primarily developed from analytical studies of near-field and far-field seismicity in Los Angeles, California. The loading protocol development may not account for the demands due to more severe, long-duration subduction interface earthquakes of the Cascadia Subduction Zone. The adequacy of the prequalification loading protocol to capture the demands imposed by subduction interface earthquakes is therefore uncertain. In addition, studies specifically examining BRB demands under such events remain scarce. This gap in understanding emphasizes the importance of further investigation on the seismic response of BRBs under subduction interface earthquake demands. This M.Sc. research project aims to examine the seismic demands imposed on BRBs in low- to mid-rise steel buildings equipped with BRBFs subjected to seismicity expected in the west coast of Canada, develop a subduction interface-consistent loading protocol, and experimentally evaluate the seismic performance of steel BRBs subjected to subduction interface earthquake demands. Five different prototype BRBF buildings are first designed under Canadian standards. A fibre-based numerical model is developed for one of the BRBFs in each building and subjected to Nonlinear Response History Analyses (NLRHA) using three suites of 11 historical records each: shallow crustal, in-slab, and subduction interface events. The results show that the largest demands imposed on BRBs pertaining to peak strain demands, force overstrength, cumulative inelastic ductility, and fatigue life, are consistently largest under subduction interface events. The results of one of the prototype buildings are then statistically analyzed to develop a symmetrically increasing, subduction-consistent loading protocol. Following the analytical evaluation, an experimental program consisting of five full-scale BRB specimens is developed. Two of the BRB specimens have been previously tested and strain-aged for two years and eight months, while the remaining three are new. Both strain-aged specimens and one new specimen are subjected to direct brace deformation histories representing two historical subduction earthquake events. The other two new specimens are tested under symmetric loading protocols: the AISC 341 loading protocol and the subduction loading protocol developed in this study. The results of the experimental tests show that BRBs subjected to symmetric loading protocols exhibit post-yield envelope behaviour that is in good agreement with each other, irrespective of protocol. BRBs subjected to direct brace deformations confirm significant strain capacity and fatigue life available in BRBs. Furthermore, BRB force overstrength can generally be reproduced by post-yield slopes of symmetric loading protocols studied here. The strain-aged BRB shows a noticeable increase in peak forces, however, additional test data is required to verify this effect, particularly since the large tensile strain generated by the monotonic push in the strain-aged BRB was not imposed in the replica new BRB.
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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 | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 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) | 0,002 | 0,001 |
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 ».