Civil Engineering Reference
In-Depth Information
TABLE 9.2
Allowable Weld Stresses
Weld Type
Stress State
Allowable Stress (ksi)
CJP or PJP
Tension or compression
0.55
F
y
CJP or PJP
Shear
0.35
F
y
Fillet (60 ksi electrode)
Shear
16.5 but
<
0.35
F
y
on base metal
Fillet (70 ksi electrode)
Shear
19.0 but
<
0.35
F
y
on base metal
Fillet (80 ksi electrode)
Shear
22.0 but
<
0.35
F
y
on base metal
If present,
∗
the shear force, acting in a vertical direction, is (see Chapter 7)
1.80
(W)
S
w
w
=
,
(9.15)
where
S
w
is the wheel load longitudinal distribution (
S
w
=
3 ft for open deck girders
or
S
w
=
5 ft for ballasted deck girders).
The resulting force per unit length of the weld (from Equations 9.14 and 9.15) is
q
f
w
2
.
q
=
+
(9.16)
The required effective area of the weld can then be established based on the allowable
weld stresses recommended by AREMA (2008) as shown in Table 9.2.
The required effective area of welds subject to horizontal shear from cyclical
flexure ranges must also be established based on the allowable weld fatigue stresses
recommended by AREMA (2008) (typically Category B or B
depending on weld
backing bar usage).
9.3 BOLTED CONNECTIONS
Bolting is the connection of steel components or members by mechanical means.
Bolted connections are relatively easy to make and inspect (in contrast to the equip-
ment and skills required for welding and inspection of welds). The strength of the
mechanical connection is affected by the bolt installation process.
9.3.1
B
OLTING
P
ROCESSES FOR
S
TEEL
R
AILWAY
B
RIDGES
9.3.1.1
Snug-Tight Bolt Installation
Connection strength depends on the bearing, shear, and tensile strength of the bolts
and connected material for bolts installed without pretension (snug-tight). The bolts
are made snug-tight manually with a wrench or power tool applied to the nut. The full
effortofapersoninstallingaboltwithawrenchoranutinstalledwithapowertooluntil
wrench impact will generally provide the small pretension required to retain the nut on
∗
For example, vertical loads are transferred through the flange-to-web weld in open and noncomposite
deck plate girder spans.
