
Seismic Demand-Capacity Analysis Framework
Systematically evaluate seismic vulnerability through demand-capacity ratios and fragility modeling
What You Can Do
You can quantify seismic vulnerability for existing buildings and new designs by calculating demand-capacity ratios, generating fragility curves, and performing nonlinear pushover analysis. This framework integrates response spectrum analysis with probabilistic seismic hazard evaluation to produce cost-effective retrofit strategies that meet specific performance objectives (Immediate Occupancy, Life Safety, Collapse Prevention) and align with current code standards like ASCE 41 and ASCE 7.
Features
Compute DC ratios for structural components and systems to quantify seismic adequacy against performance targets
Generate probability-of-exceedance curves for damage states across multiple ground motion intensity levels
Evaluate inelastic behavior using pushover procedures and dynamic nonlinear time-history analysis
Incorporate probabilistic seismic hazard assessment (PSHA) data to tailor recommendations to local ground motion characteristics
Compare alternatives and justify capital investments by ranking retrofits based on vulnerability reduction and cost-benefit ratios
Map structural performance to owner objectives (IO, LS, CP) and establish acceptance criteria
Validate designs against ASCE 41-17, ASCE 7, and jurisdictional seismic provisions
Scale analysis across building inventories for regional resilience planning
Example Output
Example 1: Demand-Capacity Ratio Report
- Soft-story frame: DC ratio = 0.68 (Life Safety limit = 1.0) → Recommend shear strengthening
- Beam-column joint: DC ratio = 0.45 → Requires joint confinement retrofit
- Foundation anchorage: DC ratio = 0.92 → Acceptable with monitoring
Example 2: Fragility Curve Output
- Collapse probability at MCE (Mean Chip Earthquake): 3.2%
- Life Safety exceedance at DBE (Design Basis Earthquake): 12% → Exceeds 10% target
- Immediate Occupancy at 475-year event: 45% → Retrofit needed
Example 3: Retrofit Recommendation
- Option A (Shear walls): Cost $2.1M, Risk reduction 68%, payback period 8 years
- Option B (Base isolation): Cost $3.8M, Risk reduction 85%, payback period 12 years
- Recommended: Option A with phased damper upgrade for acceptable risk-cost balance
What's Included
- SKILL.md instruction file with methodology and decision trees:
- Demand-Capacity Calculation Template: spreadsheet with component-level ratio computations
- Fragility Curve Framework: PSHA integration checklist and probability modeling guidance
- Nonlinear Analysis Checklist: pushover procedure setup, acceptance criteria, and validation steps
- Retrofit Comparison Matrix: cost-benefit analysis template for prioritizing alternatives
- Performance-Based Design Mapping Table: alignment of structural systems to IO/LS/CP objectives
Who It's For
- Structural Engineers evaluating existing buildings or designing new structures in seismic zones
- Retrofit Consultants comparing strengthening alternatives and justifying capital investments
- Post-Earthquake Assessment Teams conducting rapid safety evaluations and damage quantification
- Facility Managers prioritizing seismic upgrades across building portfolios
- Municipal Engineers developing community resilience and seismic risk mitigation strategies
Best For
- Seismic vulnerability assessments of existing buildings against current code standards
- Post-earthquake damage evaluation and safety determinations
- Retrofit planning and cost-benefit analysis for performance-based upgrades
- Fragility and risk analysis for portfolio-level decision-making
- New construction design optimization in Seismic Design Categories D, E, and F







