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
Fa = Short-Period Site Coefficient
Fv = Long-Period Site Coefficient for a period of 1.0 seconds
SMS = Short-period design spectral response acceleration parameter [dimensionless]
SM1 = Design spectral response acceleration parameter for a period of 1.0 seconds [dimensionless]
SS = 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
SD1 = Design spectral response acceleration parameter for a period of 1.0 seconds
SDS = 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 Fa and Fv 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, Fa
Site Class | Ss ≤ 0.25 | Ss = 0.5 | Ss = 0.75 | Ss = 1.0 | Ss = 1.25 | Ss ≥ 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 | |||
F | ||||||
Long-Period Site Coefficient, Fv
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 | |||||
F | ||||||
