Civil Engineering Reference
In-Depth Information
Table 3.1 Characteristic Values for Vertical Load Models SW/0 and SW/2 of Standard
Load Model
q
vk
(kN)
a (m)
c (m)
SW0
133
15.0
5.3
SW2
150
25.0
7.0
In the United States, design live train loads recommended by the Amer-
ican Railway Engineering and Maintenance-of-Way Association
(AREMA) [1.25] are based on the Cooper E80 loading as shown in
Figure 3.3
. The 80 in E80 refers to the 80 kip (1 kip is equal to
4.448 kN) weight of the locomotive drive axles. An E60 load has the same
axle locations, but all loads are factored by 60/80. New bridges may be
designed to carry E90 or E100 loads. The designated steel bridge design live
load also includes an “Alternate E80” load, consisting of four 100 kip axles,
which is shown in
Figure 3.4
. This load controls over the regular Cooper
load on shorter spans. AREMA [1.25] also presents formulas for the calcu-
lation of the impact, which is the dynamic amplification of the live load
effects on the bridge caused by the movement of the train across the span.
The design impact values are based on an assumed train speed of 60 mph. It
should be noted that the steel design procedure allows the reduction of the
calculated impact for ballast deck structures. Different values for impact from
116.75 kN/m
Figure 3.3 Cooper E80 live loading of standard trains specified in AREMA [1.25].
Figure 3.4 Alternate E80 live load of standard trains specified in AREMA [1.25].
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