trestle construction over rivers

[fran1942]

Hello, can someone please give me advice as to trestle construction over rivers.
I am modelling 1900 circa. I was wondering what the common construction method was back then for building trestle bridges that spanned small-medium rivers. eg. a river in a canyon or gully.
Would the "bents" stop either side of the river, or would the bents continue as normal and be sunk into the river bed.
I hope I am making myself clear.
In other words, I want to know if bents would be sunk into a river bed, or whether the trestle bridge would form a gap where the river passed under them and then continue with bents on the other side of the river ?
Thanks for any advice and / or pics.

 

[MasonJar]

It depends on how wide the river is. Spacing of trestle bents does not vary much, but you can put a bridge section (or otherwise vary the construction) across the river if it is too wide.

Andrew

 

[Doc Holliday]

fran,
I'm modeling the same era as you. Here's a link to a pic showing two trestles and a plate girder bridge over a lake on my layout.
http://www.the-gauge.com/showthread.php?t=14193
I used mid-span rock foundations and bents for the girder bridge. The low trestle sits on piles sunk directly into the river. Trestle bents normally wouldn't go into the water. Piles are driven into the bottom and then a pile cap is built on top. The pile cap is what actually supports the trestle bent. I originally planned for the tall trestle in the back to span a river so built it with the middle section without bents. When the river grew into a lake, one bent on each side ended up in the water. If you look carefully you can see where the bent rests on the black lake bottom. I'll probably go back and add a stome foundation.
Doc

 

[nachoman]

many things to consider here - would this river see large boat traffic? You mention that yours is small/meduim in a canyon so I would guess not. Is this a curved trestle or straight? steel trusses (common by 1900) can span a few hundred feet between bents. I would guess engineers would avoid putting a support in the middle of a river whenever possible. A typical construction would be a short approach plate-grider bridge at each end with a longer truss in the center. trestles are never curved - "curved" trestles are really a bunch of short straight sections with curved track on them.

 

[Gary Pfeil]

I don't know much about the engineering of bridges in general but always thought that what Doc said about trestle bents not ordinarily going into water was logical. Here's a link to a bridge I lived near back in the early 80's, and its not just because the water is high that the bents are in the water. http://www.the-gauge.com/showthread.php?t=3483&page=3

 

[Will_annand]

Fran, that depends on the river and on the railway.

Here is a photo of the main bridge on the credit river in the area of my layout.
Circa 1884.

 

[60103]

If you go to Harper's Ferry, there is a situation where there is a long wood trestle along the Shennandoa but the bridge over the Potomac is on masonary piers. There is a picture from the civil war era showing where the original bridge has been destroyed and the still piers are in the river. The replacement bridge has a steel deck.
In trestles, if the river is narrow enough there may be a bridge element made out of timber spanning the river. Design and depth will depend on various factors, including river traffic, if any. I wouldn't make it long than 2 or 3 regular bent spacings.
If the river is non-navigable, you could put bents into the river bottom, if it's suitable. This would probably apply to mountain streams, not the Ohio.

 

[railwaybob]

Hello fran1942. If you visit these pages on my website, you can see a real trestle that was being built in 1912 for the Canadian Northern Railway at Chaffey's Locks, Ontario Canada. http://www.railwaybob.com/ChaffeysLocks/02Trestle01.htm

You will clearly see the cross sections of the bents. If you look closely enough, you will see a horse being used to haul the pieces of lumber into place, along with a small "donkey" steam engine doing the same thing. There are about 5 people poised at each deck of the trestle, ready to do their bit in incorporating the lumber into the trestle.

If you think that the above trestle might be a bit too tall, click on this link to see a couple of trestles that are only about 30 feet above the ground.
http://www.railwaybob.com/BandW/BandWPage06.htm
These trestles were originally constructed in 1889 for the Brockville, Westport & Sault Ste Marie Railway, renewed in 1899, but weren't filled in until 1915. Not only do these trestles cross a small gulley, but there's also a steel bridge which crossed the very busy Grand Trunk Railway mainline at Brockville, Ont.

During the period 1912- 1914, trains of flat car loads of steel rails would be hauled across the BW&SSM trestles up the line to the Canadian Northern Railway line that you see under construction in the first link. Can you imagine what might have happened if those trestles had collapsed!?

While the trestles and the steel bridge have long disappeared, the GTR line is now a very busy Canadian National Railways Toronto - Montreal main line - but that's another story.

Enjoy!