Performance of seismically deficient existing braced steel frame structures with flexible diaphragms
Bibliographic record
Abstract
Concentrically-braced frames (CBFs) are among the most common seismic force resisting systems (SFRSs) used in Canada and across the world. In single-storey applications, these braces are often paired with a flexible steel diaphragm as a means of effectively transferring the seismic forces through the SFRS. Seismic loads are determined using the 2010 NBCC, while the design and detailing requirements for CBFs are provided by the CSA S16-09 Standard. The capacity design philosophy is used, in which one element in the SFRS is designed to undergo large inelastic deformations in the event of a strong ground motion; for a CBF, this fuse element is chosen as the braces. The CSA S16-09 ensures that the fuse element exhibits the necessary amount of ductility and energy dissipation to withstand the large deformations imposed by the earthquake. Structural elements surrounding the fuse element are protected in such a way that the gravity load resisting system remains elastic after such an earthquake so that occupants have time to evacuate. The seismic provisions in the NBCC and S16 have greatly evolved over the past fifty years. In particular, the capacity design philosophy was not employed in design between 1960 and 1970. As such, it becomes difficult to predict the seismic performance of existing structures designed and constructed within that time period. The seismic performance of structures designed using the 1965 NBCC and CSA S16-65 is examined using the open-source structural analysis software OpenSees. Model accuracy is achieved through the calibration of the material parameters obtained through the physical testing of existing brace specimens with the OpenSees model. Incremental dynamic analyses are performed on 32 prototype structures. Seven failure criteria for net-section fracture, bolt shear, block shear, bearing failure and drift limitations are used to determine the performance level of the prototype structures using a methodology similar to that found in FEMA-P695.%%%%Les cadres a contreventements concentriques en acier (CCC) sont parmis les systemes de resistance de forces sismiques (SRFS) les plus utilises au Canada et a travers le monde. Dans les edifices unietagaires, ces contreventements sont souvent couples avec une diaphragme flexible en acier comme methode de transmission des forces sismiques a travers du SRFS. Les charges sismiques sont determines en utilisant le NBCC 2010, et la conception et les details pour le CCC sont donnes par le CSA S16-09. La philosophie du conception des capacites est utilise, ou un element fusible est choisi dans un SRFS – pour CCC, les contreventements – est concu et detaille pour ecouler dans l'evenement d'un fort mouvement du sol. La norme CSA S16-09 assure que l'element fusible demontre la quantite necessaire de ductilite et de dissipation d'energie pour resister aux grandes deformations imposees par le seisme. Les elements structuraux qui sont autour de l'element fusible sont proteges de telle maniere que le systeme de resistance de gravite reste elastique apres un tel…
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".