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[quote]QUOTE: Originally posted by beaulieu [quote]QUOTE: Originally posted by futuremodal Ballasted bridge decks - wasn't that a Milwaukee idea?[^] If you have ever been to Spokane WA, take a look at the RR bridges downtown. The NP apparently chose to go with thinner bridge beams compensated by more frequent support struts. I am sure thicker beams existed at this time, but it was probably cheaper to go with the thinner beams and increased struts. I would think this concept could be applied in other areas, aka if railroads could get away with it they would prefer their bridges over highways to have more strut support (and allowing thinner beams) rather than having to span the entire roadway. For bridges, the gross consist weight is more paramount than the point of contact weight. I also use this example for the thinner vs thicker rail debate. [/quote] That may be a case of not wanting to raise the level of the roadbed and being unable to reduce the clearances over the highway. Did you ever wonder why floor joists are on edge rather than laid flat? Because they are stiffer on edge than flat . The same is true with bridge beams. A taller cross sectioned beam will provide greater weight carry capacity than the equivilent amount of steel in more but smaller beams. [/quote] There are a few main arterials wherein the older strut support bridges were replaced by full length side girder bridges, which kept the road clearances the same as before but allowed for full width of the roadway below. On the rail issue, aren't European rails lighter than NA rails? If you look at European freight operations, their heavy haul freight cars do have bogies of three or more axles. I think that is the basis for my premise that spread axles on US railcars would allow for using lighter rail concurrent with heavier gross car loads, and thus allow our shortlines to continue viability. And some of their heavy freights run in triple digit speeds!
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