Eccentric braced frames: seismic response and design challenges
Bibliographic record
Abstract
Eccentrically Braced Frames (EBFs) are widely used to resist lateral forces, leveraging ductile design principles to reduce seismic demands. However, the current New Zealand Steel Structures Standard (NZS 3404) provides limited guidance for computing deformation demands, overlooking variability of inelastic behaviour along the frame height and potentially leading to inaccurate seismic performance assessments. The provisions also disregard the contribution of post-yield stiffness by adopting an elastic–perfectly plastic link response, which can underestimate the load-carrying capacity of EBF systems. This study evaluates the seismic performance of multi-storey EBFs through nonlinear pushover analyses of an eight-storey case study, developed using an experimentally validated finite element model. Predictions from design provisions and an alternative analytical method are benchmarked against the nonlinear results, focusing on displacement profiles, storey drift demands, link rotations, and the influence of base rotational stiffness, post-yield stiffness, and shear link length. The findings show that while standard methods provide acceptable accuracy in the elastic range, they fail to capture redistribution of plastic demands in the nonlinear regime. The results also demonstrate that parameters such as base rotational restraint and strain-hardening can significantly influence the seismic response of EBF systems, highlighting the need for advanced design methodologies to provide more accurate seismic design.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 teacher head, 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".