Ground amplification coefficient

The ground amplification coefficient, S, takes the following value: For ρ·ab <= 0,1g ⇒ S= C/1,25; for 0,1g < ρ·ab <0,4g ⇒ S=C/1,25 + 3,33(ρ·ab/g-0,1)(1-C/1,25); for 0,4g <= ρ·ab ⇒ S=1. Being: C: Ground coefficient, ab: Basic seismic acceleration, ρ: Dimensionless coefficient of risk. It takes the value ρ=1.0 for constructions of normal importance, and ρ=1.3 for constructions of special importance.