Civil Engineering Reference
In-Depth Information
15
"
3 #9 bars
(3.00 in.
2
)
18
"
3
"
10
"
Figure 3.10
Computing Value of
t
A
s
f
y
0.85
f
(3.00)(60,000)
(0.85)(4000)(10)
5.29 in.
a
c
b
1
0.85 for 4000 psi concrete
c
a
1
5.29
0.85
6.22 in.
t
d
c
15
6.22
6.22
(0.003)
(0.003)
0.00423
0.004
0.005
c
Beam is in transition zone and
from Figure 3.5
0.48
83
t
0.48
(83)(0.00423)
0.83
d
a
2
15
5.29
2
M
n
A
s
f
y
(3.00)(60)
2223.9 in. k
185.3 ft
M
n
(0.83)(185.3)
153.8 ft- k
PROBLEMS
3.1
What are the advantages of the strength design
method as compared to the allowable stress or alternate
design method?
For Problems 3.7 to 3.9 determine the values of
t
,
, and
M
n
for the sections shown.
Problem 3.7
(
Ans.
M
n
379.1 ft-k
3.2
What is the purpose of strength reduction factors?
Why are they smaller for columns than for beams?
3.3
What are the basic assumptions of the strength design
theory?
24
"
27
"
3.4
Why does the ACI Code specify that a certain mini-
mum percentage of reinforcing be used in beams?
4 #9 bars
3.5
Distinguish between underreinforced and overrein-
forced beams.
3
"
f
y
= 60,000 psi
f
c
= 4,000 psi
3.6
Explain the purpose of the minimum cover require-
ments for reinforcing specified by the ACI Code.
12
"
