# Gurder Bridge Spans?



## John J (Dec 29, 2007)

Does anyone know the average span of a gurder bridge? 

OR in other words 

What is the average distance between towers when you see these multi tower gurder bridges? 

JJ


PS Got some interesting irons in the fire. Will post if things turn out the way I think they should


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## jake3404 (Dec 3, 2010)

Thats kind of a loaded question. I am going to try to explain this in terms of prototypical standards and you can adjust to model... 

A prototype has to determine what the tonnage that will be used on the bridge being built. If the tonnage expected is low they may extend the girders longer. If heavy tonnage expected, well, then the distance between towers is shorter. However, many railroads will look at between a 40 ft span and a 80 ft span. 

Ok I lied, as far as modeling, I would look into a scale 40' span. It gives you a little more to the bridge. I think your in 1:29 so that scales out to 1' 4" approx. between towers. If you did 80' between towers then it stretches out to 2' 9" between towers. Thus less towers and less detail to the bridge.


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## John J (Dec 29, 2007)

Thanks for the reply 
I looked at some pictures and it looks like is some instances it is a little over the lengh of a SD-45 or SD40-2 
But that may just look that way 
That is why I asked the question. 
NN


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## Trains West (Oct 4, 2008)

plate-girder has been used as short as 15 ft and as long as 200 ft ( built in 1976) 

stanard " factory " sort of bridge is 20 ft / 30 ft / 50ft / 70 ft/ 90 ft 


in models it is better to use shorter multables to make it look right then it would be to do a whole 200 ft run in one bridge


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## John J (Dec 29, 2007)

Posted By Trains West on 18 Feb 2011 03:22 PM 
plate-girder has been used as short as 15 ft and as long as 200 ft ( built in 1976) 

stanard " factory " sort of bridge is 20 ft / 30 ft / 50ft / 70 ft/ 90 ft 


in models it is better to use shorter multables to make it look right then it would be to do a whole 200 ft run in one bridge 


I was thinking shorter multipul spans like you suggest. I am going to make some reall frail looking towers.


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## denray (Jan 5, 2008)

JJ 
This is where you need your cnc plasma they work great at cutting out these type of steel piers, maks them quick and looks good 
Dennis


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## chaingun (Jan 4, 2008)

JJ, 
You said what I do in another thread - do what looks right. Can't wait to see what ya got cooking! 
Best,Ted


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## livesteam53 (Jan 4, 2008)

JJ ... 

Be sure and post some pictures.


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## Totalwrecker (Feb 26, 2009)

JJ,
Your desire for spindly towers requires shorter spans.
After reading this thread I opened google and went a learnin'.
Seems a plater girder bridge is 1/15 height to length...meaning a 15' span is 1' tall, a 30' is 2''tall and so on. Plate steel is heavy and adds up quickly.
My only question is how this fits with your modern rolling stock? Short/ spindly is olde tyme engineering.

John


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## jake3404 (Dec 3, 2010)

Posted By Totalwrecker on 19 Feb 2011 09:16 AM 
JJ,
Your desire for spindly towers requires shorter spans.
After reading this thread I opened google and went a learnin'.
Seems a plater girder bridge is 1/15 height to length...meaning a 15' span is 1' tall, a 30' is 2''tall and so on. Plate steel is heavy and adds up quickly.
My only question is how this fits with your modern rolling stock? Short/ spindly is olde tyme engineering.

John


Also it has to be wider at the bottom than at the top


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## John J (Dec 29, 2007)

I did this as a tempoary thing.

I don't have a good picture becasue it is rather crude and not some of my best work 

It will work till I do something better.

It's the ugly thing off the the right in the picture I runs down the middle of the layout 

It's a reversing loop. 

Marty did some great towers on the Hi line.












JJ


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## John J (Dec 29, 2007)

Did a search for Plate Girder bridges and came up with a lot more information than before. 
Got some great pictures. 
JJ


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## SteveC (Jan 2, 2008)

John

Here's a link to a Google book (remember DOWNLOAD







) maybe it will be of some help.

The Practical Design of Plate Girder Bridges[/b]


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## rdamurphy (Jan 3, 2008)

Personally, my own opinion, if I were going to build a large steel bridge like that, I'd go all out, and have deck bridges on the approaches, then plate girder bridges, with a large warren truss or something similar in the middle. 

I would recommend _Model Railroad Bridges and Trestles_ from Model Railroader. It goes into great detail, lots of pics. Great book. You can get it from Amazon for about 10 bucks. 

Thanks! Robert


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