Civil Engineering Reference
In-Depth Information
Check No. 3 @ 10 in. (required shear reinforcement above 2nd floor):
A
st
=
2
×
0.13
×
8
=
2.08in.
2
2.08
96
60
4
0.020
⎛
⎜
⎞
⎟
ω=
×
16
128
α=
4
=
0.021
96
×
16
×
c
w
=
0.020
+
0.021
)
+ 0.72
= 0.054
(
2 0.020
128
2.08
⎛
⎜
⎞
⎟
(
)
M
n
=
0.5
×
2.08
×
60
×
96 1
+
1
−
0.054
/12
=
957ft
−
kips
×
60
( )
= 861ft − kips > M
u
= 580ft − kips O.K.
φ
M
n
=
0.9 957
No. 3 @ 10 in. (required shear reinforcement) is adequate for moment strength above the 2nd floor.
(3) Design for flexure in N-S direction
Initially check moment strength for required vertical shear reinforcement No. 4 @ 10 in.
(see Example 6.4.2)
(a) For 1-20 ft-8 in. wall segment at first floor level:
A
st
= 4.96 in.
2
P
u
= 279 kips
M
u
= 4060 ft-kips
˜
w
= 248 in.
h
= 8 in.
For No. 4 @ 10 in.:
A
st
=
0.24
×
20.67
=
4.96 in.
2
4.96
248
60
4
=
⎛
⎜
⎞
⎟
ω=
0.038
×
8
2.79
248
α=
4
=
0.035
×
8
×
c
0.038 + 0.035
2 0.038
w
=
)
+ 0.72
= 0.091
8"
(
279
4.96
⎛
⎜
⎞
⎟
(
)
M
n
=
0.5
×
4.96
×
60
×
248 1
+
1
−
0.091
/12
=
5415 ft
−
kips
×
60
(
)
= 4874 ft − kips > M
u
= 4060 ft − kips
φ
M
n
=
0.9 5415
O.K.
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