Civil Engineering Reference
In-Depth Information
The bolt tension, T B =
T
+
T Q , with substitution of Equations 9.32 and 9.33, is
w b t p F y
4 a
+ αη
M f ( 1
+ ηα
)
M f ( 1
+ ηα
)
+ αη
M f
a
T B = T + T Q =
=
b
b
T 1
.
αη
b
=
+
(9.34)
( 1
+ αη
)a
Therefore,
T
.
αη
b
T Q =
(9.35)
( 1
+ αη
)a
Further manipulation of these equations provides the thickness, t p ,as
4 T B ab
t p
b)) .
(9.36)
w b F y (a
+ αη
(a
+
However, Equations 9.34 through 9.36 are difficult to use in routine design. Analyti-
cal and experimental studies have provided a semiempirical equation as (Douty and
McGuire, 1965)
w b t p / 30 ab 2 A b
0.50
.
T Q =
T
w b t p / 6 ab 2 A b
(9.37)
a/b ((a/ 3 b)
+
1 )
+
Equation 9.37 may be further simplified as (Kulak et al., 1987)
T 3 b
.
t p
20
T Q =
8 a
(9.38)
Further analytical and empirical studies (Nair et al., 1974) have provided other empir-
ical equations for the prying force, but Equation 9.38 is simple and conservative for
use in routine design of bolted connections subjected to tension.
Connections with bolts subjected to direct tension should generally be avoided in
the main members of steel railway superstructures. Bolt tension and prying may occur
combined with shear in connections such as those shown in Figures 9.10a and 9.10b.
AREMA (2008) recommends the allowable tensile stress on fasteners, including the
effects of prying, as 44 and 54 ksi for A325 and A490 bolts, respectively.
9.3.4.1.1.5 Allowable Combined Tension and Shear Stress in Connections
Connections in steel railway superstructures may be subjected to combined shear and
tension forces (e.g., the beam connection of Figure 9.10b).An ultimate strength inter-
action equation developed from tests (Chesson et al., 1965) is shown in Figure 9.15
 
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