Civil Engineering Reference
In-Depth Information
Wheel
Rail
d'
b
>6˝
Tie
Rock ballast
2
d
b
Concrete slab
1
(3
'
+
d
b
) but < 5
'
Longitudinal distribution to deck
§ Track
Tie
2
d
b
1
Length of tie +
d
b
Lateral distribution to deck
FIGURE 4.17
Longitudinal and lateral distribution of live load to the deck on ballasted deck
bridges.
where
P
is the portion of axle load on the transverse beam;
A
is the axle load;
S
is the
axle spacing, ft;
D
is the effective beam spacing, ft, which
• for bending moment calculations with a concrete deck, is
D
=
d
1
1
+
(d/aH)
0.4
,
√
H
12
1
d
+
+
d
or
S
.
• for bending moment calculations with a steel plate deck, or for end shear in
both concrete and steel decks, is
but
D
≤
D
=
d
,
