Civil Engineering Reference
In-Depth Information
Detailed design of a tension flange
:
I
x
n
c
t
≥
M
t max
F
all
M
t max
0.55
F
y
≥
9814
(
12
)
0.55
(
50
)
≥
4282 in.
3
(
OK, 4469 in.
3
provided
)
S
x
n
=
≥
for Category B weld;
M
max
-range
F
fat
(
6032
)(
12
)
16
4524 in.
3
(
OK,
S
x
n
≥
≥
≥
∼
1% overstress with
4469 in.
3
provided
)
.
A subsequent check on the net section is required after the detailed design
is completed.
Detailed design of a compression flange
:
Brace frames will be placed at equal intervals of 11.25 ft
5.55
E
L
p
r
c
y
=
11.25
(
12
)
4.67
=
28.9
≤
F
y
≤
134 OK,
(
11.25
)(
12
)
4.67
2
0.55
(
50
)
2
6.3
F
call
=
0.55
(
50
)
−
=
27.5
−
0.64
=
26.9 ksi,
2
(
29,000
)
π
or
π
(
29,000
)(
50.0
)
(
11.25
)(
12
)(
90
)(
√
1
0.13
F
call
=
=
42.8 ksi.
+
0.3
)
Since
F
call
≤
0.55
F
y
≤
27.5;
F
call
=
26.9 ksi
I
x
g
c
c
≥
9814
(
12
)
26.9
M
c max
F
call
4378 in.
3
(
OK, 4965 in.
3
provided
)
.
S
x
g
=
≥
≥
Vertical buckling of the compression flange is avoided by precluding
flexural buckling of the web when
f
c
F
cr
≥
0.18
(
85
)
50
29,000
0.18
h
F
y
E
9814
(
12
)
/4965
26.9
0.64
23.7
26.9
t
w
≥
≥
≥
0.60 in.
(
OK, 0.625 in. provided
)
.
Local buckling of the compression flange
:
The plate girder will have ties directly supported on the top (compression)
flange; therefore
0.35
E
b
2
t
f
=
20
2
(
2.50
)
=
4.0
≤
F
y
≤
8.4 OK
