Collapse Safety Assessment of Steel Multi-storey Buildings with Friction Sliding Braced Frames and Backup Moment Resisting Frames as a Dual System
Bibliographic record
Abstract
In the early 1980’s, Concordia University’s library building saw the first application of cross-braced Pall friction dampers (PFD). Although PFDs have evolved and improved, including the friction material used, development of the design procedure has been limited. Using a recently proposed force-based design method and considering detailed computational and modeling techniques, three types of seismic force resisting systems are presented herein: the bare Friction Sliding Braced Frame (FSBF), Friction Sliding Braced Frame with Continuous Columns including gravity columns (FSBF-CC) and Dual FSBF system (D-FSBF). Installing backup MRFs in parallel with a primary FSBF can provide the structure with load path redundancy and elastic-frame action, while taking advantage of the large energy dissipation capacity of PFDs. \n \nThe objectives of this research are three-fold: 1) to develop an accurate nonlinear model for PFD that is capable of bearing and failure, 2) to quantify the ductility-related force modification factor, Rd, for the proposed seismic force resisting systems: bare FSBF, FSBF-CC, and D-FSBF and 3) assess fragility and collapse safety of low-rise and middle-rise buildings braced with the proposed seismic force resisting systems subjected to crustal and subduction ground motions. \n \nThese objectives are carried out using 2-D numerical models developed in OpenSees for 4- and 8-storey prototype buildings located on Site class C in Vancouver, B.C. A force-based design method was developed in line with NBCC 2015 and CSA/S16-14 standard requirements. Considering the similarity with buckling restrained braced frames (BRBF), design was conducted for RdRo=4 and RdRo=5. All buildings were subjected to short duration crustal and long duration subduction ground motions, and a discussion regarding the slip length demand of PFD was provided. \n \nFrom nonlinear response history analysis of 4 and 8-storey FSBF buildings (RdR0=4), it was found that the bare FSBF was structurally unstable and reached collapse prior to design level under the ground motion suites. Therefore, using the bare FSBF is not recommended. The 4-storey FSBF-CC building (RdR0=4) prevented collapse at design level, however experienced excessive residual drift, while the 8-storey FSBF-CC building reached collapse at design level under both crustal and subduction ground motions. Thus, the FSBF-CC system can be used only for low-rise buildings, but caution should be taken. \n \nUsing the Dual FSBF system composed of FSBF and a backup MRF, designed for an additional 25% base shear and two sets of RdR0 =4 and 5, it resulted that both 4-storey and 8-storey D-FSBF buildings showed sufficient margin of safety under both ground motion suites. Subsequently, when increasing the building height (e.g. the 8-storey building), the ductility-related force modification factor, Rd = 4 is recommended. The Dual FSBF system is recommended to brace low-rise and middle-rise buildings located in subduction zone, as Cascadia subduction zone, where megathrust earthquakes could occur.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.001 | 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 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".