where:

A : Maximum value of acceleration corresponding to an  specific seismic zone  
     (See Table 1, Table 2)
I : Building Importance Coefficient  (See Table 3)
Rd: Ductility factor corresponding to required ductility levels (See Table 4, Table 5)
W : Weight of the building
C : Spectral seismic coefficient given by the following formula (See Table 6).  
      The value of Ceait be less than 0.45.

C = 1 + (Fa – 1) T/T₁      0 ≦ T ≦ T₁
C = Fa                            T₁ ≦ T ≦ T₂
C = Fa (T₂/T) ^p                               T > T₂

where:

Fa : amplification coefficient depending on soil profile.
T : period of the structure
P : expectable exponent

 Soil Classification
          Soil conditions are classified into four categories in Cuba (See Table 7)