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Bridges?

18K views 129 replies 18 participants last post by  Tscarborough 
#1 · (Edited)
I've been asked to give a price on building a small bridge out of stone across a creek, maybe 10' across. I haven't gone to look yet but I'm wondering if anyone has any experience with bridge building (I don't) and has any tips about things particular to bridges to be looking for at the site. I'll be looking for signs, and asking questions about high water levels, and asking about styles wanted etc.. I guess just wondering if there's anything bridge specific as opposed to any old arch that needs to be thought about

Oh, one thing i've wondered is what are common/popular walkway materials? Obviously wood, what about concrete? i don't think asphalt, maybe flagstone or cobbles (wet set callade stonecutter) If wood, what would be the best way to attach it?and I guess it would want to be raised so that water could get away.
 
#68 ·
Not at the moment If i looked in my file I could find the drawing but I don't have it on the computer. The plan is actually more interesting. The elevation is just a bridge with an elliptical span (I REALLY want to change his mind to a segmental arch. I think that the tight part of an ellipse where it switches from the small circle to the large one will be difficut with "rustic" stone) The plan though shows that the bridge isn't straight...it's hyperbolic! Not sure how to make string hyperbolic?? There is almost no part of this thing that will be built with string, yet another thing thatn will slow things down...Not a bridge designer but I'm curious about how important it is in a small bridge like this. I can see with a larger one that as load is applied the bridge tends towards straight but this is only a 20' bridge
 
#72 ·
I posted a picture of the stone pile 1 page back. I could pull out a few individual ones and take pics if you want

the cient is open to suggestion but so far hasn't budged on the elliptical. I think he thinks that I can just put stone on top of the centre and that it will be an arch. I don't think he understands that the stones need to radiate to a point
 
#74 · (Edited)
I don't think I can work on the bridge in the spring because of the river conservation society and also because the creek will most likely be over the footings, so I should have time then....and most likely I'll be anxious to do something interesting at that point after a mind numbing winter of repetitive work
 
#81 ·
The stone style isn't finalised fully, but the basic idea is random rubble built to courses (every 18" maybe 2') but this stone has reasonable bedding planes so it won't be too random but the coursing won't be arrow straight either. As for the ellipse, his drawing shows a very fat ellipse. In FJNs post it's like the steel bridge. *couldn't link the pic for some reason) That is part of my worry, not a lot of rise for the majority of the span and also a very dramatic radius change at the end.
 
#95 ·
I wonder why so many bridges are built with eliptical arches?
It's not just bridges. They are often used for large openings where the rise is limited because of upper floor heights.
The advantage over a segmental arch is the way the weight is transferred downwards to the foundations, meaning the abutments at each side can be smaller as well. They also look better.
You often see them in town pubs over the entrance to the yard.
 
#84 ·


If I did that right there should be a drawing of the bridge. Found it while going through files for tax time

There are a few things that have changed a bit, mainly that while it would be awesome to do a cobble road with tar/pitch for a joint I just don't think it's feasible/economical. And rather than SS dowels in the footing he elected to use epoxy coated (Yes FJN I know)

And for economy reasons we are also looking at perhaps using a PCL mortar in the middle of the abutments and only using NHL 5 for the span and for the facework of the abutments. Can anyone think of any major problems that would create? I was able to get the price of the NHL down to about $26/bag but that's still almost 3x what a bag of masons lime or portland would cost, if we can save $1k or 2 that would help. But if anyone has any reason why it would create a huge issue then obviously the money will be spent on the NHL

thanks
 
#89 ·
Third easiest...

Easier to pull a wagon with livestock over....:eek:

My State Capitol has bridges with ~30 to one elliptical arches...Concrete with face brick. the secret is the end abutments have to be massive or tied into bedrock.
 
#93 ·
He poured the footings last summer and early fall. I was supposed to start the abutments last fall but we got an early winter and another project ran late so I wasn't able to get a start. He built the centres over the winter..going to be interesting to see a curved centre. There doesn't look to be a significant amount of flooding around the creek this year due to a slow melt, so hopefully I'll be able to start in the next few weeks. Sand is on site, stone is on site and my price for NHL is locked in.

We're still getting some occassional nights down close to -10c/10F, I could be working and throw an insulated tarp over everything at night but with the NHL it would worry me without a heat source. Especially since most of our days are just hitting 7c/45-50F, not much of a heat sink unless it's a real sunny day
 
#94 ·
So does anyone have an opinion about using a PCL in the centre of the abutments and only using NHL for the "face work". The entire span will be done using NHL...Only talking abutments here. I'm kind of thinking it wouldn't be unlike pouring concrete in the middle...similar to a concrete abutment with a stone face.
 
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