Western Railroad Discussion > Coopers Loading

Does the railroad civil engineering trade still use Coopers Loading to rate railroad bridge strength, or to design bridges? Like so many other mechanical engineering rules that were "the bible" prior to modern computer design methods, has this method of bridge design gone into the stone age?

And does anyone know of a web site anywhere that gives the sizes of various bridge elements (beams, trusses, etc) for various Coopers Loading numbers?

Thanks -

- Kit -


ps: I originally got into mechanical engineering to design bridges, but somehow I wound up designing satellites instead!

This link suggests that the answer is yes.

http://www.neel-schaffer.com/railroad/rr_bridgetunnel.asp

I found it by going to Google, starting with "cooper's loading," found nothing, changed to "cooper's loading railroads," found a reference to "Cooper's E railroad loading," put that in and came up with this and a couple of other possibly useful links, together with many of no value. It's amazing what someone with absolutely no knowledge of engineering can do on the internet.

Good old Google. I ran with your idea and came up with this site on the Army's railroad engineering program. Scroll down to the section titled "Bridges" for the discussion on Coopers E Loading system.

It turns out that the Coopers E Loading of a particular structure is the pounds of live load per axle it can carry.

(snip)
Although various formulas have been used to compute bridge capacity, the most accurate of these is Cooper’s E rating. In this formula, each driving axle on the locomotive carries a proportionate part of the total weight loaded on the drivers. A bridge designed to carry a 0-6-6-0 diesel-electric locomotive weighing 240,000 pounds (108,844 kilograms) on the drivers, must have a Cooper’s rating of at least E-40 (40 equals to 40,000 pounds).
(snip)


Thanks!

Looks like that web site has some more intereting engineering info too - something to read!

- Kit -

Kit,

In short, yes.

Quoting my CE 321 text,
"The loadings on railroad bridges are specified by the code of the American Railroad Engineers Association (AREA). Normally, E loads, as originally devised by Theodore Cooper in 1894, are used for design. ... Steinmann has since updated Cooper's load distribution and has devised a series of M loadings, which are also acceptable for design." (Hibbeler, "Structural Analysis (Fifth Edition)," 2002)

-Dave
BSCE '05
Rose-Hulman Institute of Technology

Agreeing with the last reply. We use Coopers un determining cover over culverts for one thing and are currently including Cooper calcs in a retaining wall design along the UP mainline in Eastern Oregon. The AREMA manual still contains several references and instances where both live and dead loads need to be figured.

rh
Spokane

The Cooper rating is very much in use. It has modifications for steam and electric traction that incorporate the effects of dynamic pounding and nosing. A lot of the old bridges built for steam are strong enough to resist our current axle loads due to the design for steam effects. Also, the RR industry is very conservative, always designing for far into the future. Now we are designing for E-80 loading. Not that anything that heavy runs now, but as these bridges last 60-100 years, we don't want them to impair future operations.

The AREMA designs now incorporate seismic factors too. We used to joke that a fast freight train was like an earthquake; not exactly correct but you get the idea of the strength of RR bridges compared to highway bridges when you learn that no RR bridges in North America have been lost due to earthquakes (tidal waves following the Anchorage Good Friday event not counted).