Page 481 - Design of Reinforced Masonry Structures

SHEAR WALLS 7.43

where S = the maximum considered earthquake (MCE), 5 percent damped, spectral
MS
acceleration parameter at short periods adjusted for the site class effects
S = the maximum considered earthquake (MCE), 5 percent damped, spectral

M1
acceleration parameter at a period of 1 s adjusted for the site class effects
Spectral parameters S and S in Eqs. (7.55) and (7.56) are determined from Eqs. (7.57)
MS
M1
and (7.58):
S = F S (7.57)
MS a s
S = F S (7.58)
M1
v 1
where S = the mapped maximum considered earthquake (MCE) spectral acceleration at
S
short periods (0.2-s period)
S = the mapped maximum considered earthquake (MCE) spectral acceleration at a
1
period of 1 s
F = short period (0.2 s) site coefficient (Table 7.2)
a
F = long period (1.0 s) site coefficient (Table 7.3)
v
Values of S and S for various regions of the United States are listed in ASCE 7-05
1
S
Figs. 22-1 through 22-14. The values of coefficients F and F vary with site class and the
a
v
values of S and S . The values of both coefficients are 1.0 for Site Class B for all values
s
1
of S and S .
S
1
TABLE 7.2 Values of Site Coefficient F a [7.13]
Mapped MCE spectral response acceleration parameter at 0.2-s period a
Site class S s ≤ 0.25 S s = 0.50 S s = 0.75 S s = 1.00 S s ≥ 1.25
A 0.8 0.8 0.8 0.8 0.8
B 1.0 1.0 1.0 1.0 1.0
C 1.2 1.2 1.1 1.0 1.0
D 1.6 1.4 1.2 1.1 1.0
E 2.5 1.7 1.2 0.9 0.9
F - b - b - b - b - b
a Use straight-line interpolation for intermediate values of S S .
b Site-specific geotechnical investigation and dynamic site response analyses shall be performed.
TABLE 7.3 Values of Site Coefficient F v [7.13]

Mapped MCE spectral response acceleration parameter at 1-s period a
Site class S 1 ≤ 0.1 S 1 = 0.2 S 1 = 0.3 S 1 = 0.4 S 1 ≥ 0.5
A 0.8 0.8 0.8 0.8 0.8
B 1.0 1.0 1.0 1.0 1.0
C 1.7 1.6 1.5 14 1.3
D 2.4 2.0 1.8 1.6 1.5
E 3.5 3.2 2.8 2.4 2.4
F - b - b - b - b - b
a
Use straight-line interpolation for intermediate values of S 1 .
b
Site-specific geotechnical investigation and dynamic site response analyses shall be
performed.