Reserve Capacity and Implications for Seismic Collapse Prevention for Low-Ductility Braced Frames in Moderate Seismic Regions
Bibliographic record
Abstract
Although there has been extensive research on achieving ductile behavior and robust performance for steel structures in high seismic regions, little is known about the behavior and performance for low-ductility steel structures that are prevalent in moderate seismic regions. The seismic lateral-force-resisting system recognized in ASCE 7 that is currently widely applied to steel structures in moderate seismic regions is the R = 3 system, where no ductile detailing is required. While not explicitly stated, the viability of an R = 3 system rests on the notion that there is some degree of reserve capacity within the system that allows design forces to be reduced when there is no ductile detailing. Reserve lateral strength, or reserve capacity, is defined as lateral force resistance that maintains structural stability after the primary lateral-force-resisting system has degraded. In general, previous studies have not investigated the global quantification of reserve capacity or local requirements for stiffness and strength of the elements comprising the reserve system. However, several potential sources of reserve capacity in these structures have been identified: connections in the gravity framing system, connections in the braced frame system, and column continuity. Another source of reserve capacity comes from within the braced frame system, in the event where a slotted HSS tube re-engages and bears upon the gusset plate in compression after the connecting fillet welds fracture in a seismic event. In this paper, the work of a multi-institution research group studying the behavior and performance of these low-ductility braced frames is presented. The research program includes connection and frame testing and analysis in conjunction with numerical simulations of building system seismic response. The following specific aspects of the research are discussed: (1) modeling and full-scale testing of beam-column gravity connections with angles; (2) large-scale testing of nonductile brace connection limit states; (3) large-scale testing of multi-story braced frames with nonductile limit states; (4) nonlinear static and dynamic analysis of buildings with nonductile braced frames. In all cases, quantifying reserve capacity and establishing the effect of reserve capacity on the system behavior are emphasized. These results provide a valuable resource for design of low-ductility steel braced frame systems to provide collapse prevention performance.
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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 | 0.001 | 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".