// multi-utility computation suite · offline · instant · precise
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sci.earthquake-response-spectrum-Sa Calculator
Calculates spectral acceleration Sa(T) from an earthquake ground motion time history using a single-degree-of-freedom oscillator with 5% damping. Design response spectra define the peak acceleration demand on structures of each natural period — tall buildings (T > 1 s) experience lower Sa than short stiff buildings.
Inputs
T Period S
Time for one complete cycle (s). Period = 1 / frequency. A 50 Hz signal has a 20 ms period.
Pga G
Rate of velocity change (m/s²). Earth's gravity: 9.81 m/s². Objects in free fall accelerate at this rate.
Zeta Pct
Reference formula or conversion factor shown for context.
Soil Class
Reference formula or conversion factor shown for context.
Results
spectral acceleration Sa (g)
The proportional relationship between two quantities.
spectral displacement Sd (m)
ISP (specific impulse) — rocket engine efficiency in seconds. Higher ISP means more thrust per kilogram of propellant consumed.
site amplification factor Fa
A dimensionless multiplier applied in the calculation.