Civil Engineering Reference
In-Depth Information
If the applied load is cyclical, fatigue must be considered. A connec-
tion such as that shown in
Figure E9.5
has an allowable fatigue shear stress
range of 16 ksi for connections subjected to greater than 2 million stress
range cycles. The connection is, therefore, acceptable with respect to fatigue
considerations.
Example 9.7
Design the bolted beam framing connection using 6
×
6
×
1
/
2 in. angles
as shown in
Figure E9.6
for a shear force,
P
=
70 kips and end moment,
M
e
=
25 ft-kip. The beam is 20 ft long and frames into the web of a plate
girder with single-shear connections. The allowable shear stress on the
high-strength bolts is 17.0 ksi. The shear force and bending moment were
developed from an analysis considering partial rigidity of the connection, so
the AREMA recommendation of a 25% increase in shear force is not used.
P
=
70 kips
M
e
=
25 ft-kips
=
300 in-kips in the direction creating tension at the top of
the beam end
Shear and Bending on Bolts in the End Section:
Bolt forces due to bending:
The centroid of the connection is
y
2
(
12
+
9
+
6
+
3
)
6.0 in.
The section modulus of the top (third row) bolts in the connection is
=
=
10
6.0
)
2
6.0
)
2
6.0
)
2
6.0
)
2
6.0
)
2
)
2
((
12
−
+
(
9
−
+
(
6
−
+
(
3
−
+
(
0
−
S
bt
=
=
30.0 bolt-in for top
(
12
−
6.0
)
bolts (in tension in the simple beam connection)
The section modulus of the second row bolts in the connection is
S
bb
=
6.0
)
2
6.0
)
2
6.0
)
2
6.0
)
2
6.0
)
2
)
2
((
12
−
+
(
9
−
+
(
6
−
+
(
3
−
+
(
0
−
=
60.0 bolt-in for bot-
(
9
−
6.0
)
tom bolts
P
P
/2
P
/2
3", typ.
0.5"
0.5"
M
e
15"
21"
y
2.5"
6"
2.5"
2.25"
Side elevation
End section
FIGURE E9.6
