Seismic behavior and design of friction concentrically braced frames for steel buildings
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Bibliographic record
Abstract
This study explores the possibility of improving the seismic response of concentrically braced frames (CBFs) by including friction connections at the end of the bracing members. These connections will slip at a predetermined load level in order to absorb and dissipate by friction most of the energy input by earthquake ground motions, and then avoid yielding and buckling of the bracing members. The characteristics of CBFs and other alternative systems are reviewed and a FCBF system is proposed which includes bolted brace connections with slotted holes in the gusset plates. 42 connection samples including various faying surface materials and bolting configurations were subjected to dynamically applied cyclic loading. These tests revealed that a stable response can be achieved by using proper sliding material together with an appropriate bolt clamping force level. The behavior of a full-scale braced frame assembly undergoing severe interstorey drifts was also investigated. The results of the quasi-static tests performed showed that the system behaves in a very predictable and satisfactory manner. An analytical study including nonlinear dynamic analyses of typical single- and multi-storey FCBFs was then performed in order to develop design guidelines for their stability under seismic loading. For single-storey buildings with a rigid roof diaphragm, design spectra were developed for predicting the ductility demand and the threshold of instability. For single-storey structures with a flexible roof diaphragm, a case study including 48 buildings revealed that this type of structure experiences more significant nonlinear response than the equivalent SDOF system. Analyses of eight braced frames varying from 2 to 12 storeys in height showed that instability in multi-storey FCBFs occurs in a collapse mechanism involving only a few stories. Such phenomena can be inhibited by providing the columns in the building with sufficient bending strength and stiffness. Values were proposed for the stiffness which appeared to yield a stable response of the frames. Columns designed solely for gravity loads were found to have sufficient strength for sustaining the moments likely to develop during ground motions. Design criteria for the brace induced column loads and for the loads acting in the collecting elements were also proposed.
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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 it