1613.3.3 Site coefficients and adjusted maximum considered earthquake spectral response acceleration parameters.
The maximum considered earthquake spectral response acceleration for short periods, S
MS
, and at 1-second period, S
M1
, adjusted for site class effects shall be determined by Equations 16-44 and 16-45, respectively:
SMS = FaSs (Equation 16-44)
SM1 = FvS1 (Equation 16-45)
where:
Ss = The mapped MCER spectral accelerations for short periods as determined in Section 1613.3.1.
S1 = The mapped MCER spectral accelerations for a 1-s period as determined in Section 1613.3.1.
Exception: When electronic values of mapped acceleration parameters are used as per Section 1613.3.1 of this code, the site coefficients, F
a
and F
v
, cannot be taken from Tables 1613.3.3(1) and 1613.3.3(2) of this code. Rather, general procedures in Chapter 11 of ASCE 7 shall be followed to determine F
a
and F
v
.
Site Class | Fa |
Site Class | Fa |
A | 0.80 |
B (V
s
measured) | 0.90 |
B (V
s
unmeasured) | 1.00 |
C | 1.30 |
D | 1.57 |
E | 2.28 |
F | Note a |
a. Site-specific geotechnical investigation and dynamic site response analyses shall be performed to determine appropriate values, except that for structures with periods of vibration equal or less than 0.5 second, values of Fa
for liquefiable soils are permitted to be taken equal to the values for the site class determined without regard to liquefaction in Section 1613.3.4.1.
Site Class | Fv
|
Site Class | Fv
|
A | 0.80 |
B (V
s
measured) | 0.90 |
B (V
s
unmeasured) | 1.00 |
C | 1.50 |
D | 2.40 |
E | 4.20 |
F | Note a |
a. Site-specific geotechnical investigation and dynamic site response analyses shall be performed to determine appropriate values, except that for structures with periods of vibration equal or less than 0.5 second, values of Fv
for liquefiable soils are permitted to be taken equal to the values for the site class determined without regard to liquefaction in Section 1613.3.4.1.