Risk-Based Life-Cycle Cost-Benefit Analysis of Seismic Retrofitting Steel Moment-Resisting Frames in Canada using Friction Devices
Bibliographic record
Abstract
Many existing steel moment-resisting frames (MRFs) in Canada constructed between the 1960s and 1980s were not seismically designed. Friction devices have shown promise to reduce the seismic damage of early-designed steel buildings by supplementing additional force, stiffness, and energy dissipation mechanisms to resist earthquake loading. However, installing friction devices for seismic retrofitting is often subjected to limited financial resources. The seismic vulnerability of early-designed buildings in Canada’s seismic zones might cause significant repair losses after future earthquakes, while the upfront retrofit cost would prevent building owners from making preventive, yet somewhat intangible, investments at present. Such a decision-making dilemma can be solved by developing a risk-based life-cycle cost-benefit (LCCB) analysis approach that assesses the economic trade-off between upfront retrofit expenses and risk-based lifetime benefits. This study conducts the LCCB analysis based on case studies to retrofit two six-story steel MRF office buildings located in Montreal and Vancouver. The steel MRFs were initially designed only for wind loads per the 1965 National Building Code of Canada (NBCC) and cannot satisfy the seismic design provisions in NBCC 2020. As such, steel MRFs are retrofitted with friction devices using the equivalent static design procedure, whereas the essential design parameters are identified and varied to cover different design scenarios. The LCCB analysis is performed for each design scenario based on a multi-step procedure consisting of seismic hazard modeling, ground motion selection, non-linear response history analyses, seismic fragility development, and life-cycle seismic loss analysis. The life-cycle benefit from each design is quantified as the reduction in seismic losses between as-built and retrofitted buildings, from which (1) the benefit-cost ratio is computed between life-cycle benefit and upfront retrofit cost and (2) the anticipated net benefit over time is developed to pinpoint the payback year where the net present value equals zero. This study systematically compares to what extent different retrofit design parameters (e.g., brace stiffness ratio, force modification factors for ductility and overstrength) would affect the life-cycle benefit-cost performance of the steel MRFs in both Montreal and Vancouver. This study provides decision-makers with a risk-based, transparent tool to assess the economic feasibility and identify the most cost-effective solution for seismic retrofitting steel MRF buildings in eastern and western Canada
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".