It's been a while since I've embarrassed myself on here by asking bonehead questions, so here's something I have been wondering about. Do railroad bridges ever occur on grades? I know that as we travel up the highways over the mountain passes here we often go under railroad bridges on lines that are at least nominally going "up" to the pass, but it's hard to tell if the bridges are actually higher at one end. Or is it the practice to level off just before crossing a river or ravine or highway or what have you, then restart the grade after the bridge? If there ARE bridges on the tilt, are there any special considerations? It seems to me that it would just be a bad idea, structurally. I'm mainly just curious, but it could bear on some future plans.
Thanks,
-Matt
Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.
This is going to be a raw guess, so don't take me to the bank. Besides, I'm just killing time prior to midnight when I become a slug.
I'd think that just as railroads try to avoid grades as much as possible, as much consistency of grade is sought when they are required. I'm suspicious that for relatively shorter spans there really is no appreciable "work savings" in making it level and there may actually be an operational liability or two. When an extended span or long viaduct is involved there may be additional factors on either end that might allow for a level and beneficial stretch.
In saving you from potential embarassment, I may have now assumed all or a portion of it! We'll see by what follows. You came looking for facts and got an opinion right off the bat. Nature of the age, Matt.
John
crossthedogDo railroad bridges ever occur on grades?
There are railroad bridges on grades in mountainous areas, and it surely occurs elsewhere as well.
I doubt very many bridges over water obstacles are on grades, unless in the mountains. As always, I am sure there are exceptions.
-Kevin
Living the dream.
2:40 am, Kevin?! No remodel projects tomorrow (today)?
I don't have any direct knowledge but maybe I can give you a bridge (sorry, bad pun) to help. The section of rail line that is about 1 1/2 blocks from my house (BNSF ex-BN exx-NP Glendive, MT to Forsyth, MT to Laurel, MT) has a grade of approximately 1% IMS. It's enough that a majority of the trains especially coal unit trains usually have two DPUs at the rear. Most people think Eastern Montana is flat but it's not. The track roughly follows the Yellowstone River. I've never explored it but I'd imagine with that grade and the river there have to be bridges that aren't laid flat no matter how hard the original track layers tried.
Hope that helps.
P.S. If you think any question is boneheaded, read my signature line.
Built in 1835 and still in use today. Not only on a grade but a curve, too:
https://en.wikipedia.org/wiki/Thomas_Viaduct
Imagine convincing the financiers back then that it would be economical to make the bridge wide enough for TWO tracks! That's called forward thinking.
Good Luck, Ed
Attuvian12:40 am, Kevin?! No remodel projects tomorrow (today)?
Generally, I stay up until 4:00-5:00 AM and sleep until noon.
I just finished working on snaking the wire for the outside security light above the garage.
and this one:
For this one, the track in the foreground curves around through a (curved) tunnel to the left, crosses the same creek on a smaller bridge uphill, and then appears going the other direction in the upper snowshed. PERFECT for the end of a peninsula. Somewhere I've seen the track grade chart of this setup, and the grade is maintained across the bridges.
I found the grade chart. The near end of the bridge is 8.2 feet higher than the far end. The bridge is 4100 feet long. Thus the grade on the bridge is .2%. The creek is 153' below the bridge.
Ed
7j43kFor this one, the track in the foreground curves around through a (curved) tunnel to the left, crosses the same creek on a smaller bridge uphill, and then appears going the other direction in the upper snowshed.
Attuvian1In saving you from potential embarassment, I may have now assumed all or a portion of it! Wink We'll see by what follows.
Thanks for the responses, all.
crossthedog Looks like you dodged a bullet, John. :) -Matt
Looks like you dodged a bullet, John. :)
One of the most famous cases, the Brusio spiral viaduct on the Bernina Railway in Switzerland...
https://en.wikipedia.org/wiki/Brusio_spiral_viaduct
SeeYou190Generally, I stay up until 4:00-5:00 AM and sleep until noon.
Same for me, Kevin, but I'm usually up by 10:00AM or 11:00AM...I think that it's probably a side-effect from shift work, where nightshifts were my favourite, followed closely by afternoons. I absolutely hated day shifts, and would trade shifts when anybody wanted to swap.We later went to 12 hour shifts, and I did almost all of mine on nights - one summer, when we were short-handed, I worked over a full month (no days off) before I got a "safety" reprimand from upper mangagement...I made a lot of money that year!
Wayne
Hint to the unwary: I think that's one of the locomotives sent to the PRR as FF2s... not a rinky-dink operation, not an inconsequential piece of railroad, and likely not an unimportant train...
Are those snowsheds at Tye?
Ed, there is someplace famous where the C&O climbed heroically out of a river valley on enormous steel trestlework that I recall as being heavily graded. Bet you have pictures.
crossthedog When I first glanced at the second photo I assumed that was a line of coal hoppers, but those are passenger cars! Where on earth could so many people be going that would require crossing a creek on switchback bridges like that?
When I first glanced at the second photo I assumed that was a line of coal hoppers, but those are passenger cars! Where on earth could so many people be going that would require crossing a creek on switchback bridges like that?
Hard to say, but the scene is along the Great Northern line from Seattle to Spokane. Well, it WAS. I believe it was deactivated when the second Cascade Tunnel was opened in 1929.
Oddly, there WAS a switchback at this location, but it was replaced by the big tunnel loop.
crossthedogDo railroad bridges ever occur on grades? I know that as we travel up the highways over the mountain passes here we often go under railroad bridges on lines that are at least nominally going "up" to the pass, but it's hard to tell if the bridges are actually higher at one end. Or is it the practice to level off just before crossing a river or ravine or highway or what have you, then restart the grade after the bridge?
It would seem to me that if the railroad was being built on a grade and it came to a place where a bridge of some kind would be needed, and the terrain on the other side was also on a grade, it would make perfect sense to build the bridge with a suitable grade included. Cutting down the terrain on that opposite side would be expensive and likely difficult, too.
I have six bridges on my layout (I know, it's only a model railroad) and all of them are on grades. Three are on grades of likely less than 1% (barely noticeable) and the other three are at about 2.9% (very noticeable).Two of the latter are on a grade that's continuous for about 45', so cutting down the grade percentage after that first bridge is crossed, the remaing grade will need to be even more severe.The other bridge, which is beneath the first one on the long grade, is at 2.5%, and like the other two, with curves in both directions.All that, on the layout, at least, calls for multiple locomotives and sometimes extra helpers, too, which makes for some interesting running.
Here's the two that are close together, but on different tracks...
...and with some serious power making the uphill run...
The track on the upper bridge, shown above, eventually comes to this one...
...the far end of which is still over 6' from the level track at the end of this grade.
I can't see any reason why the prototype would be concerned if their bridge needed to be built on a grade if the available terrain required it.
Overmod Hint to the unwary: I think that's one of the locomotives sent to the PRR as FF2s... not a rinky-dink operation, not an inconsequential piece of railroad, and likely not an unimportant train... Are those snowsheds at Tye?
The electric is a GN Y-1. Next there is a GN P-2 (4-8-2) and then likely a GN Pacific.
Nope. There were lots of snowsheds in the area then. Still are a few. A few years ago, I walked from the Essex Hotel east to a snowshed and wandered around a bit. Very impressive, of course.
Nothing particularly unusual about bridges with grades. As someone posted, there's approaches that are sloped with plate girder spans, but the longer spans (such as over a river) with trusses don't typically have grades except...maybe some very unusual retrofits where you build a bridge within a bridge so that the loads are transferred uniformly on the truss. You definitely find bridge grades in modern passenger railroad design. These can be box girder beams or traditional beams. The bridges may also slope and curve. There's one on my regular commute that just opened over a month ago around 947 W. Roscoe St, Chicago, IL that has really steep grades because the train pairs each have traction and can power up the hill in a short distance. Structural technology has rendered the old elevated tracks and bridges obsolete and Chicago is in the process of tearing down the old elevated steel tracks and replacing them with modern concrete designs like you see in DC and Atlanta. I think that's another reason they may be uncommon, because the structural systems made steep grades and curves more challenging a century ago.
Older bridges designed specificially for freight transport aren't going to change grade substantially which is why the slope may not be that noticeable.
doctorwayneI can't see any reason why the prototype would be concerned if their bridge needed to be built on a grade if the available terrain required it.
MUCH easier to accommodate this with a stone or concrete arched viaduct than with plate girders or trusses on lattice steel bents...
Starrucca Viaduct (Lanesboro, PA) is on the grade coming down from Gulf Summit on the Erie. Been over that one on a freight train in my Conrail days...