Deleted
LINK to SNSR Blog
I turned the page on my train calendar for this year and found another photo of the Cuttingsville Bridge, a.k.a. "that weird bridge in Vermont". To see my images at full resolution you have to open and close once, then open it again. Not that it shows any more detail than the other pics we've seen here, but it's still pretty cool enlarged.
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.
Something like this?:
"The girder span is hanging from a cantilever off of the main truss span. I believe the other end of that same span supports another span the same way. The latter span is a truss, however; not a girder."
Ed
Something you don't see that often in railroad construction, probably because free span between supports is usually maximized, is full use of cantilever structure supported at 'quarter points' of the moment diagram.
Now that I see TF's blown-up detail shots, I wonder if the weird trusswork in the 'middle' of the main truss isn't a sort of reverse cantilever: you have a small inverted truss sitting centered on a pier, with an inverted truss to either side bearing on it -- this would save the steel for the bottom web, a major part of the cost in the era of those fancy but spindly Phoenix Bridge designs (like those for New York elevated trains built with machinery at high speed as Sullivan documented...)
Then the deep plate span probably has a box end sitting on similar inverted construction... ???
Yeah, I don't know the details of the connection of the three spans of the Cuttingsville bridge. And I surely would like to.
They are NOT rigidly connected. The natural bending of the structure would cause the connection to fail.
But it is surely not obvious how it's done.
Just very interesting! I keep looking at pictures for how it's "hinged", and not finding it. I even looked up from below on Google. It LOOKS like it's not hinged, but it has to be.
7j43k Track fiddler Technical specs. on bridge horizontal forces, weight shifts, expansion and contraction and vertical forces caused by heavy train loads is of great interest here. Rotation is very minimal but it is there. The rotation happens with ANY load; it's just a matter of degree. It even happens without any added load from traffic.
Track fiddler
Technical specs. on bridge horizontal forces, weight shifts, expansion and contraction and vertical forces caused by heavy train loads is of great interest here.
Rotation is very minimal but it is there.
The rotation happens with ANY load; it's just a matter of degree. It even happens without any added load from traffic.
BEAUSABRE 7j43k This type of bridge is certainly not common for railroads. I had a quick look for a US version, and nothing came up. North American examples. Mallery states that every railroad bridge across the Missisipi south of Memphis was cantilever, with other significant examples being the Niagara, Poughkeepsie and Quebec (longest span RR bridge of any type) Bridges
7j43k This type of bridge is certainly not common for railroads. I had a quick look for a US version, and nothing came up.
North American examples. Mallery states that every railroad bridge across the Missisipi south of Memphis was cantilever, with other significant examples being the Niagara, Poughkeepsie and Quebec (longest span RR bridge of any type) Bridges
And for those who want a picture, here's one at Thebes, Illinois:
showing at the center is a cantilever span. In my opinion, it is the part that looks like it COULD serve as a free-standing bridge. Then there is the funny section that goes back to the pier. That is what the cantilever span is hung from. Notice the size of the big up-rising member, from the pier towards the center. This supports all/most of the weight of the cantilever span. Hence its sturdiness, reminiscent of our new favorite bridge. What has me going is that there's a short "bonus section" between where it feels like the support for the cantilever span ends, and the span itself starts. Pretty much the section between the silvery-painted plates in that area.
Here's an even weirder looking part of the bridge. It LOOKS like there's a missing pier. Actually, I think they're doing just the same thing as happened on our bridge--the last truss spans are "semi-cantilever". Note the similarity of the framing with that of the center span:
I'll throw a couple of cents in.
That 'center' span looks like it's intended as an indeterminate truss, like the bridge at Kenova. And I would be not have been surprised to find a pin-and-hanger arrangement to the end span (I have never liked those after having missed going into the Mianus River on one by no more than hours).
More interesting is the reason for what appears to be timbering around that small end span. Perhaps an enclosure for maintenance, or sheathing as for a covered bridge? Is that just a deep-web plate girder?
The 'flat' shoes provide a concentrated small-area load while distributing force over a much larger area to the masonry of the pier bearing area, and the webs of the contacting girders.
My understanding was that some trusses had pinned shoes at both ends, and expansion simply bowed the span in the middle, the same way the Hell Gate Bridge works (note the absence of structure between the arch and those stone "support" towers!)
7j43kThis type of bridge is certainly not common for railroads. I had a quick look for a US version, and nothing came up.
crossthedog Wow, I'd sure love to understand the engineering behind this.
Wow, I'd sure love to understand the engineering behind this.
You may regret getting me started.
We're talking cantilever bridges, here:
The one above is the most famous--Firth of Forth. The parts that are cantilevered are the two "teeny" truss spans connecting the giant "islands". Here's a picture of the construction:
Once the "islands" are built out from the center, the cantilevered truss spans are lifted up from barges and (carefully) installed.
Point here is that there are no piers or towers holding up those truss spans. Just the other parts of the bridge.
This type of bridge is certainly not common for railroads. I had a quick look for a US version, and nothing came up.
Anyway, the designer(s) of our beauty went a somewhat different route, though maybe not:
They did build one (1) center "island". It happened to sit on two supports (piers), rather than the big single ones in the above design. Also of note (and hard to miss) is that the project parts of the island structures "stick out" (technical term) MUCH farther than on ours. But ours still does have that "stick out".
Then two (2) cantilevered spans were placed to finish the bridge. BUT the outer ends of those two spans were NOT held up by "islands", but abutments. You could argue that they were each "half cantilevers".
Someone had to decide to build the bridge this way. As opposed to three deck spans sitting on those same piers. The outer spans can be a bit smaller/lighter, because they're not as long. That's always a plus in bridge building. The minus is that there's extra expense (and weight) in adding the "stick outs". The weight downwards on the piers probably doesn't change much. But maybe it does. I'm in no position to figure that one out.
It's also possible that this design was cheaper to install (as opposed to fabricate).
I have a short list of Favorite Bridges, and this new one is now on it! I doubt there is another rail bridge like it in the whole world. If there IS, I will be thrilled to see its picture, too.
@Ed, I see what you were saying now. I had assumed there was a fourth span, way off to the right out of sight, also a deck girder. When I figured out that there are only three spans it all made sense, including your comments. I do see the snow behind that area in the more recent photos you posted, too, which means TF's posited gusset is not what's holding the spans up, which was the point you were making about the other span. And I only now, just now, realized that the span on the right is also suspended over nothing at all. I didn't notice that at first; I assumed that right-most truss span was sitting on the right pier. Wow, I'd sure love to understand the engineering behind this.
crossthedog @Ed, the second photo, the one you posted with the RS-3 going over it, doesn't seem to show that part of the bridge, so I'm confused about what you're seeing. At least I understood TF to be describing brackets that would be appearing just out of frame to the left on your photo.
@Ed, the second photo, the one you posted with the RS-3 going over it, doesn't seem to show that part of the bridge, so I'm confused about what you're seeing. At least I understood TF to be describing brackets that would be appearing just out of frame to the left on your photo.
There is a center span of the bridge. It's the truss bridge sitting on the two piers. That bridge has some extensions built past the piers that hold up two other spans. One span is the deck girder. The other is a deck truss (as is the center span).
It is true that the photo I brought in does not show the support for the deck girder, but it does show the inside face of the member supporting the other span (the truss). Looking at that picture, I don't see anything added to the inside face of that diagonal member (that goes up to offer compressive support for the end of the other truss).
It's true that the end supporting the girder span COULD have the "gusset" addition as TF said, but it doesn't show at the other end of the center span. Bridge design tends to be symmetrical. Of course, with the different loading implied by the different outer spans, this might not be true in this case.
Here's another photo of the bridge that is more revealing. Note that there's snow where the gusset should be.
You can tell from the following view that this ain't no little kid wimp bridge:
Built 1895. So, since anything older than 100 years is ancient infrastructure that must be replaced (see also Brooklyn Bridge), that thing is over 25 years due for collapsing. YIKES!
PS: If I hadn't have seen it, I would have said no one ever built such a thing. Man, do I LIKE that bridge!
Track fiddlerI drew an exaggerated illustration of bridge rotation this morning.
I searched for a while and couldn't find better photos of the deck part of the bridge. I guess people think it's the less interesting/less scenic bit.
-Matt
Here's a picture of that connection from a different angle. There doesn't appear to me to be an added "gusset plate" onto that member.
It IS very large and heavy. Keep in mind that it is taking the entire compressive load of half of the other span, plus any load on that half.
Track fiddler Technical specs. on bridge horizontal forces, weight shifts, expansion and contraction and vertical forces caused by heavy train loads is of great interest here. Rotation is very minimal but it is there.
crossthedog Track fiddler Bridges are interesting. Fiddler, I'll say they are. How about this one in Cuttingsville, Vermont? I can't even figure out how the deck girder part of this bridge is supported.
Track fiddler Bridges are interesting.
Fiddler, I'll say they are. How about this one in Cuttingsville, Vermont? I can't even figure out how the deck girder part of this bridge is supported.
SWEET!!!
That bridge is way cool Dog And it's also cool to see a more modern looking bridge of the era with stone piers.
I was zooming in over coffee this morning and it was very vague to see the connection detail that very much interested me. Somewhat baffling for a while but I do believe the bridge attaches with a huge gusset plate bracket up the diagonal column fanning out horizontally.
I would be led to believe that gusset plate may have some sort of reinforcement on the back which would be interesting to see.
It appears black in the photograph almost like a shadow. Couldn't be a rivet counter today.
I drew an exaggerated illustration of bridge rotation this morning.
P.S. Wish I had room on my layout to add THAT BRIDGE! I would love to build it.
TF
Wow, so cool!
The girder span is hanging from a cantilever off of the main truss span. I believe the other end of that same span supports another span the same way. The latter span is a truss, however; not a girder.
Yup. Never seen nuthin' like thet before!
Track fiddlerBridges are interesting.
His sleeves are rolled up and his hands are dirty.
He's good! He's very, very good.
gmpullman 7j43k Seems like the plates would have to be lubricated, REGULARLY. A two-man job: Erie Bridge Supports by Edmund, on Flickr Regards, Ed
7j43k Seems like the plates would have to be lubricated, REGULARLY.
A two-man job:
Erie Bridge Supports by Edmund, on Flickr
Regards, Ed
If those things are made in a similar fashion to steam turbine base and sole plates, there is a grease groove (or grooves) machined into the mating surface of one of the plates. One end of the groove has a grease fitting, and the other has a plug that is removed during the greasing process. This acts as a vent.
What I'd really like to know is how that guy with the white shirt and tie manages to not get a spot of grease on him. In 34 years of working around turbines I couldn't walk within 10 feet of one without getting a smudge somewhere.
That must be a publicity photo.
Track fiddler It was explained to me it is why the larger bridges have split shoes with the pin in the middle and I'm sure the roller shoes work in the same way.
It was explained to me it is why the larger bridges have split shoes with the pin in the middle and I'm sure the roller shoes work in the same way.
I think not.
The roller shoes are meant to allow movement. The pin type does not, and so is used at the rigid end (except, as you have pointed out, for rotation about the pin).
I think the purpose of the split shoes with pin is to make for easier assembly. You just have to place the pin in the already in-place bottom piece, and lower the bridge (with the top piece already attached) downwards. The bridge, being properly designed and fabricated, will line up beautifully.
If you use the other style (the not-split), you either have to insert the pin(s) from the side while holding the bridge up just-so, or you have to have the bridge shoe fully assembled and in place, and you then lower the bridge down and insert a multitude of bolts.
I have seem both of these two latter processes done on container cranes, where the trucks are added to the bottom of the crane during installation. It is NOT the favorite part of the job for the crew--highly stressful.
Track fiddler gmpullman Erie Bridge Supports by Edmund, on Flickr Huh. And here I thought it would be a heavy grease and they'd have to jack up the bridge a bit to get it in-between there It comes in a cylinder bucket fed by gravity from a spicket? Must be Kroil then,...Good wonderful stuff! Seeking lubricant. TF
gmpullman Erie Bridge Supports by Edmund, on Flickr
Huh. And here I thought it would be a heavy grease and they'd have to jack up the bridge a bit to get it in-between there
It comes in a cylinder bucket fed by gravity from a spicket?
Must be Kroil then,...Good wonderful stuff! Seeking lubricant.
I do believe that is an air line coming in from the lower left.
BEAUSABRE 7j43k I never would have thought there were so many words related to bridges: To get the genuine hiding, I recommend Paul Mallery's "Bridge and Tresrle Handbook" (Paul gave me a copy back in the Sixties) I'm sure he addresses bridge shoes Bridge & Trestle Handbook by Paul Mallery soft cover Revised edition 1976 Red Co | eBay
7j43k I never would have thought there were so many words related to bridges:
To get the genuine hiding, I recommend Paul Mallery's "Bridge and Tresrle Handbook" (Paul gave me a copy back in the Sixties)
I'm sure he addresses bridge shoes
Bridge & Trestle Handbook by Paul Mallery soft cover Revised edition 1976 Red Co | eBay
See earlier post in this topic:
7j43k From Paul Mallery's "Bridge & Trestle Handbook": "One end of a simple bridge is always fixed in place, but the other end is permitted to move as the bridge expands or contracts as the temperature changes....For short-span bridges (60' (18m) or less) often the expansion-end shoe merely slides on the pedestal and both may be as simple as steel plates." 60' is, in HO, 8". The book has gone through 4 editions, and is an excellent book on the subject. Ed
From Paul Mallery's "Bridge & Trestle Handbook":
"One end of a simple bridge is always fixed in place, but the other end is permitted to move as the bridge expands or contracts as the temperature changes....For short-span bridges (60' (18m) or less) often the expansion-end shoe merely slides on the pedestal and both may be as simple as steel plates."
60' is, in HO, 8".
The book has gone through 4 editions, and is an excellent book on the subject.
7j43kSeems like the plates would have to be lubricated, REGULARLY.
7j43kI never would have thought there were so many words related to bridges:
The roller bridge shoes are interesting Ed. You can see they serve their purpose not only for support but more importantly for movement as you stated.
Definitely the movement is minimal but a critical factor shoes provide from season to season otherwise as you also stated the bridge would fail.
It would be interesting to have time lapse photography for a year and watch it in about 30 seconds and I do believe that's the only way you would ever see it. Minimal but it is there.
This could have already been stated here but It really floored me when I learned 5 - 6 years ago that bridges cause rotation at the shoes. My response, I said "Get Out Of Here!" It takes place on most but even more prevalent on the longer truss bridges.
It was explained to me it is why the larger bridges have split shoes with the pin in the middle and I'm sure the roller shoes work in the same way. The person explaining it to me went on to say put a long board in-between two saw horses and bounce up and down on it for a year and see how worn the board ends resting on the saw horses become.
I then understood how heavy freight trains going over a bridge bow the center down causing bridge rotation. Extremely minimal but must be accounted for.
Bridges are interesting.
P.S. I could be wrong but I think I remember reading the split bridge shoes with the pin in the middle have an oval stamped through the lower one to provide for expansion and contraction. Makes me wonder how often those pins have to be lubricated or changed out?
crossthedog Ed, those roller shoes look exactly like trouble waiting to happen. They look positively slippery. I hear the cartoon "slipping on a banana peel" bongo drum roll when I look at those, especially the blue cylinder. But I guess they can't really roll very far.
Ed, those roller shoes look exactly like trouble waiting to happen. They look positively slippery. I hear the cartoon "slipping on a banana peel" bongo drum roll when I look at those, especially the blue cylinder. But I guess they can't really roll very far.
Nope. The other end is firmly anchored. The rolling action is severely constrained.
My bridge is a GN bridge. I should be able to find one around here in Seattle.
I believe a railroad deck girder bridge is not noticeably railroad specific. Not a lot of styling options.
Now, through girder bridges.....
Brent, Ed, gosh, thanks for all those great photos. Brent, I love the rail idea. Got plenty of that handy. Ed, those roller shoes look exactly like trouble waiting to happen. They look positively slippery. I hear the cartoon "slipping on a banana peel" bongo drum roll when I look at those, especially the blue cylinder. But I guess they can't really roll very far.