1 MARCH 2000
f. AREMA Standard Fatigue Stress Cycles. For fatigue, the standard AREMA design assumes stress
cycles from 100 trains per day, with 150 cars each (loaded up to 315,000 lb gross weight), traveling at
speeds up to 60 mph, every day for 80 years.
g. Design Live Loads.
(1) As the standard AREMA fatigue loading is exceptionally high for most military railroad lines,
designers should use the design live loading in table 7-3, which is based on the recommendations in
chapter 15, part 9 of the AREMA Manual. This loading is a general recommendation for span lengths up
to about 75 ft. Actual design live loading may be adjusted to accommodate span length, structure design
characteristics, and other variables.
Table 7-3. Recommended Cooper Design Load for Bridges
Recommended Cooper Design Load for Car Capacity up to:
0 to 5
5 to 15
Note: 1 million gross tons approximately equals 7,600 loaded 100-ton cars or 5,300 loaded 140-ton cars.
(2) Traffic over most military railroad bridges does not exceed 5 MGT per year, thus the 0-5 MGT
category of table 6-8 usually applies. To exceed this lower level, a bridge would have to experience an
average annual passage of 38,000 loaded 100-ton cars (104 per day) or 26,500 loaded 140-ton cars (73
per day) throughout the life of the bridge.
h. Walkways. When bridges are located in areas where switching movements are made and at other
locations where it is either useful or necessary for people to walk alongside a train (or cut of cars),
walkways must be provided on at least one side of a bridge. Where people must have access to both
sides of the track when a bridge is occupied, walkways must be provided on both sides. (Workers must
never be expected to cross the track by going under cars, crossing over couplers, or climbing over cars).
i. Tie Pads. On open deck bridges, installation of rubber tie pads between the tie and tie plate is