Civil Engineering Reference
In-Depth Information
y
2
)
2
4
( y
2
)
2
and the bolt tension
4
( y
1
+
+
on the most highly stressed bolt,
σ
t
(bolt farthest from the neutral axis of the bolt
group), is
Peh
b
i
A
b
I
b
=
Pe( y
1
+
y
2
)
σ
t
=
4
( y
1
+
( y
2
)
2
A
b
.
y
2
)
2
+
If
y
Pe/
10
yA
b
. Prying action effects, which will increase the
bolt tension, must also be considered in the connection design (e.g., by using
Equation 9.38).
=
y
1
=
y
2
,
σ
t
=
9.3.4.3.1.3 Combined Shear and Tension
The bolts in Figure 9.19 are subject
to shear force,
F
bv
= τ
b
A
b
, and tensile force,
T
B
=
T
Q
, which must be com-
bined to determine the allowable stress in the bolts of the connection. The allowable
shear stress for combined shear and tension in a slip-resistant connection is (from
Equation 9.45)
T
+
f
bv
1
,
F
bv
A
b
≤
(T
B
)
(T
bP
)
f
bv
=
−
(9.55)
where
f
bv
is the allowable bolt shear stress for slip-resistant connections,
T
B
=
T
Q
is the total bolt tensile force,
T
bP
is the bolt pretension (see Equation
T
+
Example 9.5
Review the design of the slip-resistant single shear plane connection shown
in
Figure 9.19
using 7/8 in. diameter A325 bolts for a load,
P
=
55 kips with
eccentricity,
e
=
6 in. The steel is ASTM A709 Grade 50 with
F
y
=
50 ksi and
F
u
=
65 ksi. The connection geometry is similar to Figure 9.19 with:
y
=
y
1
=
y
2
=
4.0 in.
4.5 in.
w
b
i
=
=
x
4.0 in.
a
=
1.5 in. (see
Figure 9.14)
b
=
4.25 in.
t
p
=
0.5 in.
n
b
=
10 (number of bolts)
n
s
=
1
Shear
P
n
s
n
b
A
b
=
55
(
1
)
10
(
0.60
)
=
τ
bv
=
9.2 ksi
