Civil Engineering Reference
In-Depth Information
t
st
=
1.75 in.
t
sb
=
1.00 in.
b
sb
=
8 in.
The area of the splice is 1.75
(
20
)
+
51.0 in.
2
2
(
1.00
)(
8
)
=
35.0
+
16.0
=
≥
50 in.
2
OK
(
35.0
)(
4.375
)
+
(
50
)(
2.25
)
+
(
16.0
)(
0.5
)
51
y
t
=
5.25
−
=
5.25
−
2.71
=
2.54 in.
+
50
y
b
=
2.71 in.
0.46 in. from
the top flange centroid (0.46 in. farther from the girder neutral axis), the
moment of inertia at the splice will be greater than the moment of inertia
of the cross section being spliced.
The spliced flange eccentricity
Since the top flange splice centroid is 2.54
−
(
1.75
+
2.5
/
2
)
=−
0.46 in. This eccentricity creates a maxi-
mum force bending moment of 1031.5
(
0.46
)/
12
=
39.5 ft-kips, which is small
(0.45% of maximum moment) and, therefore, acceptable without further
consideration.
Check bearing stress
=
1333.7
64
(
1.00
)(
1.00
)
=
σ
bc
=
20.8
≤
f
B
ksi
l
e
F
u
2
d
b
=
(
1.5
)(
65
)
2
(
7
/
8
)
f
B
=
=
55.7 ksi
assuming a minimum loaded edge distance of 1.5 in., OK
or
f
B
=
1.2
F
u
=
1.2
(
65
)
=
78 ksi
Tension flange splices
For the splice cross section to be at least equal to the flange net cross
section
(
50
40 in.
2
)
,try
−
4
(
1.00
)(
2.5
)
=
t
st
=
1.75 in.
t
sb
=
1.00 in.
b
sb
=
8 in.
The net area of the splice is 1.75
(
20
−
4
(
1.00
))
+
2
(
1.00
)(
8
−
2
(
1.00
))
=
40 in.
2
OK
The girder net section moment of inertia is
40.0 in.
2
28.0
+
12
=
≥
2
4
(
1.00
)(
2.5
)(
43.75
)
2
185,163 in.
4
I
n
=
223,444
−
=
223,444
−
38,281
=
and the neutral axis is 50
(
88.75
)
+
53.13
(
45
)
+
40
(
1.25
)/(
50
+
53.13
+
40
)
=
48.1 in from the underside of the bottom flange.
The girder allowable tensile bending capacity is
M
tall
=
0.55
(
50
)
(
185163
/
48.1
)/
12
=
27.5
(
3849.5
)/
12
=
8822 ft-kips.
