Civil Engineering Reference
In-Depth Information
Figure 5.4
Calculating
a
,
c
,
and
t
a
105.88
60
1.76 in.
c
a
1
1.76
0.85
2.07 in.
d
c
c
24
2.07
2.07
t
(0.003)
(0.003)
0.0318
0.005
Section is ductile and
0.90
Calculating
M
n
Obviously, the stress block is entirely within the flange, and the rectangular formulas apply.
However, using the couple method as follows:
Lever arm
z
d
a
2
24
1.76
23.12 in.
2
M
n
T
z
(0.90)(360)(23.12)
7490.9 in.- k
624.2 ft- k
EXAMPLE 5.2
c
Compute the design strength for the T beam shown in Figure 5.5 in which
f
4000 psi and
f
y
60,000 psi.
SOLUTION
Checking
A
s
min
3
4000
60,000
A
s
min
(14)(30)
1.33 in.
2
nor less than
(200)(14)(30)
60,000
1.40 in
2
k
A
s
10.12 in.
2
OK
