Need to add bridge shoes - are they easy to make?

[7j43k]

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

 

 

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:

 

 

 

Ed

[Track fiddler]

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.  

 

Etc. Etc. Etc.

And your point was?.....Last time I checked ANY train or bridge is heavy. 

 

Sure glad I welcome you back to the forum last summer after you were gone so long.  I missed ya

 

 

You did provide a better image of the bridge that allows a better close-up view Ed.

 

But then you advanced to one of the world's most complex bridges still drowning here while someones describing the water.  There was no closure of the connection of the truss and the girder bridge yet.

 

 

 

The gusset plate does not go under the girder but my morning speculation from a very blurry photo had some truth to it.

 

It's an inverted double intersection Warren truss that creates a cantilever end.  Like any truss all the weight is supported on the truss ends that have gusset plates connecting angled and horizontal members.

 

Not in this case though, the weight is distributed on the opposite end of the cantilever because the bridge is inverted.  But it appears by the close up of the photo the gusset plates do not extend down the angled member but they are still there like they always are. 

 

The gusset plates have a lot to do with the girder bridge supported from the truss bridge whether the engineers designed some kind of rectangular box structure in-between them or not.  I'm sure they utilized the perpendicular member to be a big part of it.  Too bad that view it's not viewable.

 

 

This connection from your photo on the main span over the river I wouldn't even begin to play guessing games with.

 

 

 

 

TF

[7j43k]

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.

 

Ed

 

 

 

[Overmod]

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... ???

[7j43k]

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

[crossthedog]

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.

[ROBERT PETRICK]

Deleted