Layouts and layout building

In my opinion having a train cross a dam is not prototypical.  There are several reasons.  The strength of a dam is to withhold the water pressure from the lake behind it not vertically.  A railroad train weighs far more than a streetcar or road traffic as referenced by others and would crush the dam.  Train vibration would probably exceed the ability of a dam to absorb the vibrations or cause cracking of the concrete - not good.  If there was such an animal the train would probably be required to cross at a dead slow speed to reduce the vibration.  There are numerous locations where the road does not cross the top of the dam but has a separate bridge.  Glen Canyon dam comes to mind.  In fact currently there is a downstream bridge being built at Hoover Dam to eliminate the bottleneck the road creates.

 I'm not sure I agree. There is a dam in Kentucky where a railroad crosses it:

http://en.wikipedia.org/wiki/Kentucky_Dam

http://www.explorekentuckylake.com/KentuckyDam/kentuckydam.htm

 Properly constructed there should be no engineering issues.

ndbprr:

In my opinion having a train cross a dam is not prototypical.  There are several reasons.  The strength of a dam is to withhold the water pressure from the lake behind it not vertically.  A railroad train weighs far more than a streetcar or road traffic as referenced by others and would crush the dam.  Train vibration would probably exceed the ability of a dam to absorb the vibrations or cause cracking of the concrete - not good.  If there was such an animal the train would probably be required to cross at a dead slow speed to reduce the vibration.  There are numerous locations where the road does not cross the top of the dam but has a separate bridge.  Glen Canyon dam comes to mind.  In fact currently there is a downstream bridge being built at Hoover Dam to eliminate the bottleneck the road creates.

A dam is built massively - it has to be to hold back that weight of water.  The engineer designing the structure also have to consider possible earth tremors, and many areas of the continent do feel a little bit of vibration.  It doesn't matter if they only happen every 50 years and don't even rattle the pots, the dam must be able to withstand it.  Concrete railroad bridges easily withstand vibrations for the trains, and a solid concrete structure will be even less affected. 

Roads have been located along the top of quite a few dams.  The usual reason for later building a separate road bridge is to add extra lanes as traffic became busier.  Space on the dam crest is the problem, nothing to do with vibration or the extra weight.  Sometimes it is also to improve the road alignment to eliminate a dangerous corner turning onto the bridge.  This is one reason for a railroad across a dam being uncommon, simply that the topography will not allow a workable alignment.  The other reason being that most times the railroad was built long before the dam was planned.

I expect in the case of the picture just posted that the lake formed by the dam flooded the original railroad alignment, and the cheapest solution was to reroute the tracks across the new dam.  The single track of a railroad easily fits on the top and takes advantage of the existing strength of the structure.  A place where the railroad crossed a dam for this reason was the Shand Dam at Belwood Lake north of  Fergus, Ontario.  The branchline has since been abandoned and the grade is now a trail across the dam, but you can find it on Google Earth.

John 

 You are right John - I had forgotten about the Shand Dam in Belwood. I used to live about 10 minutes away in Guelph!

 The Milwaukee Road was here first, the dam came second, not exactly running on the dam itself but it proves that because of lack of room, things like this can happen. The is the branch line up to Metaline Falls Idaho.

http://www.railpictures.net/viewphoto.php?id=282387&nseq=2893

 If I recall the Lock Raven Dam north of Baltimore, they ran the railroad in front of the spillway until sufficient material is built up to finished the thing. Then they tore up the track and went away.

Conowingo is built very strongly. Under there be turbines to generate power. Those things has to be isolated and ride smooth and perfect all the time no matter what happens else where.

Many dams along the Dalles in Oregon were mighty dams but had provision for shipping ways to lift and drop ships so that they can pass through.

Hoover dam is a favorite of mine, a technical challenge for trucking. I understand it's still curing and setting up after being poured all these years ago. It might be another 100 years before it's finally all dried out and set. I think they are building a bypass bridge now.

And as I always said.. the fish come along and hit the wall underwater...

DAM!

One other thing. The English came up with a way to break the dams in Germany during world war two. There be lessons on how to break em proper in the history books by skipping bombs to them.

Heck I remember a bridge that was so strong that they had to bring in bombs so big as to cause a earthquake in that valley near the abutments. It finally dropped the monster.

Then there are bridges in Vietnam that never were really dropped.

I can go on, but dont want to burn any bridges.

Stopped today and took a photo of the dam that I am planning to model:

In this prototype, a road crosses the dam. In mine the tracks will, and I will also need to build it curved instead of straight.

Aralai:

I have a double track that crosses a river on my layout. Originally I was going to build a wooden trestle and then thought about either a small coffer or flood control dam or just building a small hill around the tracks. I am leaning toward the dam idea, as there is a dam near where I live that I'd like to model. I know that prototypically it is rare to have a track crossing a dam and even rarer to have double tracks, but I think it might be an interesting element. Here is a shot of the area. I have done a bad photoshop job to try to get even some idea of what a dam might look like. Any feedback on other ideas of how you might treat this area?

I think that's a pretty interesting idea... could have entertaining side-effects too...

Missus: "What in tarnation are you doing down there?"

Aralai: "I'm playing with the dam trains!"

jwhitten:

I think that's a pretty interesting idea... could have entertaining side-effects too...

Missus: "What in tarnation are you doing down there?"

Aralai: "I'm playing with the dam trains!"

lol