Input Data
Enter hazard, structural, and exposure values. Then calculate risk to place the output above this form.
Example Data Table
| Scenario | Site Class | Ss (g) | S1 (g) | SDS (g) | Cs | Base Shear (kN) | Risk Band |
|---|---|---|---|---|---|---|---|
| Low-Rise School | C | 0.72 | 0.24 | 0.53 | 0.110 | 940 | Moderate |
| Hospital Tower | D | 1.10 | 0.48 | 1.03 | 0.138 | 2,553 | High |
| Warehouse | B | 0.35 | 0.12 | 0.23 | 0.060 | 420 | Low |
| Soft Soil Residential Block | E | 0.95 | 0.40 | 0.57 | 0.149 | 1,340 | Elevated |
Formula Used
This calculator is intended for early-stage engineering screening, budgeting, and comparative scenario studies. It does not replace detailed code checks, nonlinear analysis, or site-specific geotechnical investigations.
How to Use This Calculator
Enter the project and site details first. Choose the structural system to preload a typical response modification factor, then adjust it if your design basis differs.
Provide hazard inputs using mapped or code-based spectral accelerations, Ss and S1. Select the correct site class because soil amplification can materially change SDS and SD1.
Fill in structural properties such as damping, importance factor, period, seismic weight, and available lateral capacity. These values drive base shear demand and the demand-capacity ratio.
Add exposure variables including vulnerability, nonstructural contents factor, annual exceedance probability, and replacement value. These support the estimated repair ratio and annualized loss outputs.
Press the calculate button. The result block appears below the header and above the form, followed by a Plotly chart, summary metrics, and export buttons for CSV and PDF.
Frequently Asked Questions
1) What does the risk score represent?
The score is a screening index from 0 to 100. It combines hazard intensity, demand-capacity ratio, vulnerability, probability of exceedance, and importance. It helps compare scenarios quickly, but it is not a legal design approval metric.
2) Why are site coefficients Fa and Fv important?
Fa and Fv adjust mapped shaking to reflect soil behavior. Soft soils often amplify motion, especially at longer periods. That can increase design spectra, base shear, damage expectation, and estimated economic loss.
3) What is demand-capacity ratio?
Demand-capacity ratio compares estimated seismic demand against available lateral resistance. Values below 1.0 generally indicate reserve strength in this screening model. Values above 1.0 suggest closer review, strengthening, or refined analysis.
4) Can I use this for final code compliance?
No. This tool supports preliminary engineering judgment and scenario ranking. Final compliance should use the governing building code, project-specific load paths, detailing rules, dynamic characteristics, and qualified professional review.
5) How should I choose vulnerability and contents factors?
Use lower values for robust, regular, well-detailed facilities with limited fragile contents. Use higher values for older, irregular, poorly detailed structures or buildings with sensitive equipment, partitions, cladding, and critical interiors.
6) Why does damping affect seismic risk?
Higher damping reduces dynamic response by dissipating energy. In this model, increased damping lowers the adjusted seismic coefficient and base shear demand. That can improve performance indicators and reduce expected repair costs.
7) What does annualized loss mean?
Annualized loss is the expected average yearly economic loss. It multiplies the estimated repair cost by the selected annual exceedance probability. It is useful for comparing retrofit priorities, insurance studies, and portfolio planning.
8) Why does the calculator show performance levels?
Performance levels provide a practical interpretation of the calculated demand and damage indicators. They translate numerical results into understandable states such as immediate occupancy, life safety, or high collapse risk.