Civil Engineering Reference
In-Depth Information
11.5.4 Example Problem
For this example problem, assume the following:
●
The subsurface exploration revealed that the site is underlain by soft sedimentary rock
that has an average shear wave velocity
V
s
1
2300 ft/s.
●
Seismic zone
4.
●
Design earthquake conditions: maximum moment magnitude
M
w
7, SR
5 mm/yr,
and distance to seismic source
3 mi.
To develop the response spectrum, the following data are utilized:
1.
Soil profile type
(
Table 11.1
): For soft sedimentary rock that has an average shear
wave velocity
V
s
1
2300 ft/s, the soil profile type is S
C
(see Table 11.1).
2.
Seismic source type
(
Table 11.4
): Since the maximum moment magnitude
M
w
7 and
SR
5 mm/yr, the seismic source type is A (see Table 11.4).
3.
Seismic coefficient C
a
(
Table 11.2
): Entering Table 11.2 with soil profile type
S
C
and zone 4, the value of
C
a
0.40
N
a
.
Entering Table 11.3 with seismic source type
A
and distance to the seismic source
3 mi, the value of
N
a
1.2. Therefore, the value of
the seismic coefficient
C
a
0.40
N
a
0.40(1.2)
0.48.
4.
Seismic coefficient C
v
(
Table 11.5
): Entering Table 11.5 with soil profile type
S
C
and zone 4, the value of
C
v
0.56
N
v
.
Entering Table 11.6 with seismic source type
A
FIGURE 11.11
Response spectrum in terms of the spectral acceleration
g
versus the period of vibra-
tion (in seconds) for 5 percent system damping using the data from the example problem in Sec. 11.5.4.
