Calculator Inputs
Formula Used
This calculator converts the entered acceleration into standard SI units, then applies engineering adjustment factors to estimate an equivalent inertial demand.
Higher mass increases force directly, but g force depends on acceleration and factors, not mass alone. Use project-specific code values whenever design compliance matters.
How to Use This Calculator
- Enter the supported mass in kilograms.
- Type the peak ground acceleration from tests, code maps, or measured motion.
- Select the matching acceleration unit before calculation.
- Apply importance, response, damping, vertical, direction, and safety factors.
- Add support count to estimate force demand per support.
- Enter allowable lateral capacity if you want a utilization check.
- Click the calculate button to view the result above the form.
- Download the summary as CSV or PDF when needed.
Example Data Table
| Case | Mass (kg) | PGA (g) | Importance | Response | Damping | Safety | Design g | Force (kN) |
|---|---|---|---|---|---|---|---|---|
| Mounted control panel | 250 | 0.18 | 1.00 | 1.20 | 0.95 | 1.10 | 0.2257 | 0.5535 |
| Mechanical skid | 800 | 0.25 | 1.15 | 1.30 | 0.90 | 1.15 | 0.3864 | 3.0319 |
| Process vessel | 1500 | 0.35 | 1.25 | 1.40 | 0.85 | 1.20 | 0.6248 | 9.1928 |
| Instrument rack | 75 | 0.12 | 1.00 | 1.10 | 1.00 | 1.05 | 0.1386 | 0.1019 |
Frequently Asked Questions
1. What does seismic g force mean?
It shows acceleration demand as a multiple of normal gravity. A value of 0.30 g means the component may experience lateral acceleration equal to thirty percent of gravity.
2. Is seismic g force the same as total force?
No. G force expresses acceleration severity. Total seismic force also depends on mass. Two systems under the same g level can have very different force demands.
3. Why is peak ground acceleration not enough alone?
Raw PGA does not reflect importance, amplification, damping, or added conservatism. Design decisions often require adjusted demand values rather than direct measured acceleration only.
4. What does the damping factor change?
It modifies acceleration demand based on energy dissipation assumptions. Better damping can reduce equivalent demand, while poor damping may justify higher adjusted acceleration values.
5. Does increasing mass change the g reading?
No. G force comes from acceleration and adjustment factors. Increasing mass raises the equivalent inertial force, but the g value itself remains unchanged.
6. Why calculate force per support?
Support sharing gives a practical estimate of anchor or pedestal demand. It helps compare total force against individual connection capacity during preliminary design checks.
7. Can this replace structural code checks?
No. This tool is useful for quick engineering estimates and screening. Final design should follow the governing code, project criteria, and a qualified engineer’s judgment.
8. Which acceleration unit should I use?
Use the unit from your source data. If your report lists values in g, keep g selected. Choose m/s², gal, or ft/s² only when your input matches those units.