Site Coefficients per ASCE 7-16 with ideCAD

How does ideCAD define site coefficients, according to ASCE 7-16?

The site class is chosen by the user.

According to ASCE 7-16 Section 20.3. 1, site response analysis must be performed for F site classes.

Spectrum parameters are determined automatically using Equations 11.4-3 and 11.4-4.

SYMBOLS

F_a = Short-Period Site Coefficient
F_v = Long-Period Site Coefficient for a period of 1.0 seconds
S_MS = Short-period design spectral response acceleration parameter [dimensionless]
S_M1 = Design spectral response acceleration parameter for a period of 1.0 seconds [dimensionless]
S_S = the mapped MCER spectral response acceleration parameter at short periods as determined in accordance with Section 11.4.2,
S₁= the mapped MCER spectral response acceleration parameter at a period of 1 s as determined in accordance with Section 11.4.2
S_D1 = Design spectral response acceleration parameter for a period of 1.0 seconds
S_DS = Design earthquake spectral response acceleration parameters at short periods

Site Coefficients

In ASCE 7-16 Table 20.3-1, the soil class is determined according to the top 100 ft (30 m) of the soil profile. It has been defined as six classes, from A to F , according to Table 20.3-1.

Depending on the site classes defined in ASCE 7-16 11.4-1, site coefficients F_a and F_v are given in Table 11.4-1 and Table 11.4-2. Straight-line interpolation is performed for intermediate values of site coefficients in the tables.

Short-Period Site Coefficient, F_a

Site Class	S_s ≤ 0.25	S_s = 0.5	S_s = 0.75	S_s = 1.0	S_s = 1.25	S_s ≥ 1.5

Site Class	S_s ≤ 0.25	S_s = 0.5	S_s = 0.75	S_s = 1.0	S_s = 1.25	S_s ≥ 1.5
A	0.8	0.8	0.8	0.8	0.8	0.8
B	0.9	0.9	0.9	0.9	0.9	0.9
C	1.3	1.3	1.2	1.2	1.2	1.2
D	1.6	1.4	1.2	1.1	1.0	1.0
E	2.4	1.7	1.3	11.4.8	11.4.8	11.4.8
F	11.4.8

Long-Period Site Coefficient, F_v

Site Class	S₁ ≤ 0.25	S₁ = 0.2	S₁ = 0.3	S₁ = 0.4	S₁ = 0.5	S₁ ≥ 0.6

Site Class	S₁ ≤ 0.25	S₁ = 0.2	S₁ = 0.3	S₁ = 0.4	S₁ = 0.5	S₁ ≥ 0.6
A	0.8	0.8	0.8	0.8	0.8	0.8
B	0.8	0.8	0.8	0.8	0.8	0.8
C	1.5	1.5	1.5	1.5	1.5	1.4
D	2.4	2.2	2.0	1.9	1.8	1.7
E	4.2	11.4.8	11.4.8	11.4.8	11.4.8	11.4.8
F	11.4.8