I guess an old flatbed trk. trl. could be an instant bridge.Might be a bear to handle though.Im likin the chained to a tree idea.In most of the logging woods around here a low water crossing is about all you get.Sometimes you got ta wait for the water ta go down to cross.Keep us posted
Concrete Foundations for Wooden Bridge
- Thread starter glennmac
- Start date
- Views: 37300
scruffy
Veteran Member
- Joined
- Jul 8, 2000
- Messages
- 1,445
- Tractor
- None (at present)
My Pa-in-Law used a 90 foot railroad flatcar to bridge his creek, it was the access road to the house. The span was only around 50feet, but a 60 foot flatcar did not allow enough 'anchor' at each end. The creek would rise as much as 12 feet in the wintertime. He had a guy with a D-8 CAT drag it two miles up the road and blade the approaches to make it level with the roadbed...that was 16 years ago, and its still there. No concrete, piers, or anything underneath, but alot of cussin' by me when I laid/drilled/bolted the 4X12's on it for decking.
DFB
Elite Member
- Joined
- Dec 7, 2000
- Messages
- 2,897
- Location
- Southern VT, Southern ME
- Tractor
- John Deere 4100 HST /410 FEL, R4s
I've heard that the steel frame work salvaged from a trashed house trailer can be used to make a bridge support too.
I'd figure the full length rebar reinforced wood formed trenched concrete footing rather than 8 individual sonotubes would make the best choice. I don't see a need to go below the frostline. Freestanding by itself it'll float a little (though with the weight involved it probably wont move at all) It'll be the most costly and labor intensive way to tie it together. You can attach the beams to the concrete with a reinforcing bracket like this:
As an alternative I'd also consider using ground contact approved wood beams doubled up for the footings. Either just trenched in on top of some good packed drainage stone, or on top of some sonotubes formed piers. If there is no trees around to chain it to use ground anchors and steel cable (like the utility co. uses to brace poles) to tie it down if there's a chance of water washing it away.
DFB
I'd figure the full length rebar reinforced wood formed trenched concrete footing rather than 8 individual sonotubes would make the best choice. I don't see a need to go below the frostline. Freestanding by itself it'll float a little (though with the weight involved it probably wont move at all) It'll be the most costly and labor intensive way to tie it together. You can attach the beams to the concrete with a reinforcing bracket like this:
As an alternative I'd also consider using ground contact approved wood beams doubled up for the footings. Either just trenched in on top of some good packed drainage stone, or on top of some sonotubes formed piers. If there is no trees around to chain it to use ground anchors and steel cable (like the utility co. uses to brace poles) to tie it down if there's a chance of water washing it away.
DFB
Thanks for the comments. I have considered some of the alternatives discussed.
1. I-beam. The ones I've seen are much more expensive than wood and are so heavy that they would have to be brought in by a crane or some large piece of equipment. I am limited to ole me, maybe my son, a B2910, and no way to get a heavy truck across my boggy dirt to the creek.
2. Low water crossing. I believe it would constantly erode, wash away and otherwise collapse. The soil is very soft. A low water crossing would also limit my access to dry times only. I want to cut and plant and dig over there in the spring.
3. Trailer beds. I have looked for used ones for a while and have never found any that seemed suitable. Again, weight and access are problems. Also, I really want something wider than the typical trailer bed.
4. Railroad car. Hadnt thought of that. Scruffy, if you've got an extra one, please mail it to me collect. Then, I'll live in in and forget this tractor stuff.
5. Telephone poles. This is still under active consideration. However, new ones are more expensive than the 4" x 12"s and I think the beams are almost as strong. Old ones pose the problem of finding them, transporting them, and then worrying about rot and creosote leaching into the creek.
So, I'm pretty much decided on the beam approach, and its my lack of concrete knowledge that is concerning me. There is NO WAY a concrete truck can get access to my creek. I will have to mix concrete on the spot. So, I'd like to minimize the amount of concrete.
No trees nearby for anchors. I doubt stakes would hold. You dig down about 4' and hit the water table.
All the wood I will use will be pressure treated, and I simply dont know how buoyant it would be. The lumber people dont know. They think it floats but not too well. Maybe the total weight will be sufficient to keep it in place.
Its not clear to me what fiber mesh or rebar would add to the concrete pad approach. Not weight. Would it prevent crumbling? Is that a real risk?
1. I-beam. The ones I've seen are much more expensive than wood and are so heavy that they would have to be brought in by a crane or some large piece of equipment. I am limited to ole me, maybe my son, a B2910, and no way to get a heavy truck across my boggy dirt to the creek.
2. Low water crossing. I believe it would constantly erode, wash away and otherwise collapse. The soil is very soft. A low water crossing would also limit my access to dry times only. I want to cut and plant and dig over there in the spring.
3. Trailer beds. I have looked for used ones for a while and have never found any that seemed suitable. Again, weight and access are problems. Also, I really want something wider than the typical trailer bed.
4. Railroad car. Hadnt thought of that. Scruffy, if you've got an extra one, please mail it to me collect. Then, I'll live in in and forget this tractor stuff.
5. Telephone poles. This is still under active consideration. However, new ones are more expensive than the 4" x 12"s and I think the beams are almost as strong. Old ones pose the problem of finding them, transporting them, and then worrying about rot and creosote leaching into the creek.
So, I'm pretty much decided on the beam approach, and its my lack of concrete knowledge that is concerning me. There is NO WAY a concrete truck can get access to my creek. I will have to mix concrete on the spot. So, I'd like to minimize the amount of concrete.
No trees nearby for anchors. I doubt stakes would hold. You dig down about 4' and hit the water table.
All the wood I will use will be pressure treated, and I simply dont know how buoyant it would be. The lumber people dont know. They think it floats but not too well. Maybe the total weight will be sufficient to keep it in place.
Its not clear to me what fiber mesh or rebar would add to the concrete pad approach. Not weight. Would it prevent crumbling? Is that a real risk?
Von
Veteran Member, Advertiser
Glenn,
Around here if you go to the phone co. they will let you take as many used poles that you want. I made a retaining wall out of them and just hauled them with my trailer. I have 30ft. ones that I got from the utility co. They even loaded them on a flatbed truck I was using. Said come back for more, please! I guess its hard for them to ge rid of the used ones. Some of the ones I got from the phone co. were like new, just shorter. Most are from people hitting them with their cars, and are too short to use again. As for anything leeching out of the wood, most new poles are the same as pressure treated wood. Isn't that what you are going to use anyway? Hope this helps some.
Around here if you go to the phone co. they will let you take as many used poles that you want. I made a retaining wall out of them and just hauled them with my trailer. I have 30ft. ones that I got from the utility co. They even loaded them on a flatbed truck I was using. Said come back for more, please! I guess its hard for them to ge rid of the used ones. Some of the ones I got from the phone co. were like new, just shorter. Most are from people hitting them with their cars, and are too short to use again. As for anything leeching out of the wood, most new poles are the same as pressure treated wood. Isn't that what you are going to use anyway? Hope this helps some.
DFB
Elite Member
- Joined
- Dec 7, 2000
- Messages
- 2,897
- Location
- Southern VT, Southern ME
- Tractor
- John Deere 4100 HST /410 FEL, R4s
Glenmac,
My understanding of using rebar in a pour is that it both strengthens the concrete and keeps it tied together to stop it from separating apart if and when it cracks from movement such as frost heaving or settling.
"Steel is embedded in the concrete in the form of a mesh, or roughened or twisted bars. A bond forms between the steel and the concrete, and stresses can be transferred between both components."
"If the concrete is allowed to move, stress will not exceed strain, and the concrete will not crack. If the concrete is not allowed to move, stress will exceed strain and a crack will form to relieve stress. When concrete structural members must resist extreme tensile stresses, steel supplies the necessary strength."
Hope it helps some.
Good luck with your project
DFB
My understanding of using rebar in a pour is that it both strengthens the concrete and keeps it tied together to stop it from separating apart if and when it cracks from movement such as frost heaving or settling.
"Steel is embedded in the concrete in the form of a mesh, or roughened or twisted bars. A bond forms between the steel and the concrete, and stresses can be transferred between both components."
"If the concrete is allowed to move, stress will not exceed strain, and the concrete will not crack. If the concrete is not allowed to move, stress will exceed strain and a crack will form to relieve stress. When concrete structural members must resist extreme tensile stresses, steel supplies the necessary strength."
Hope it helps some.
Good luck with your project
DFB
hayden
Veteran Member
Glenn,
If you want the supports to not shift around with winter frost you will need to sink your supports 3-4 feet down to get below the frostline. If you want this approach, I'd do four piers with sona tubes at each of the bridge corners.
Will your four stringers/beams be evenly spaced or will they be doubled up, two on the left, two on the right? I'm trying to figure out if one pier can support two beams? If not, you could put a beam between the two piers then set the stringers/long beams on the shorter cross beams. This will conserve concrete as opposed to doing four piers at each end of the bridge.
Since you are using pressure treated lumber, if the banks are reasonably flat I'd put the piers at the extreem ends of the beams to get them as far back from the banks as possible, but set them flush with the ground so the beams are in contact with the ground from the pier to the edge of the bank to gain some extra support.
If you don't care about frost shiting of the bridge, I'd do rectangular pads at each end, again flush with the ground level, and make them 6" or maybe 8" thick.
Either way I'd use rebar in the cement to prevent cracking/breakage.
As for anchoring the timbers to the cement, foundation bolts work (bolts that have hooks rather than wrench heads, and you sunk the hook into the cement before it sets), and I've used galvanized rafter framing plates before. These are flat rectangular plates with a bunch of nailing holes and are used to splice to buts ends of framing lumber by spanning the joint and nailing to the two pieces. I've put a few galvanized nails throught some of the holes and set the plate in the cement so half of it is standing up along side where the beam will go. Once the cement is set, place the beam in place and nail to it through the nailer holes.
If you want the supports to not shift around with winter frost you will need to sink your supports 3-4 feet down to get below the frostline. If you want this approach, I'd do four piers with sona tubes at each of the bridge corners.
Will your four stringers/beams be evenly spaced or will they be doubled up, two on the left, two on the right? I'm trying to figure out if one pier can support two beams? If not, you could put a beam between the two piers then set the stringers/long beams on the shorter cross beams. This will conserve concrete as opposed to doing four piers at each end of the bridge.
Since you are using pressure treated lumber, if the banks are reasonably flat I'd put the piers at the extreem ends of the beams to get them as far back from the banks as possible, but set them flush with the ground so the beams are in contact with the ground from the pier to the edge of the bank to gain some extra support.
If you don't care about frost shiting of the bridge, I'd do rectangular pads at each end, again flush with the ground level, and make them 6" or maybe 8" thick.
Either way I'd use rebar in the cement to prevent cracking/breakage.
As for anchoring the timbers to the cement, foundation bolts work (bolts that have hooks rather than wrench heads, and you sunk the hook into the cement before it sets), and I've used galvanized rafter framing plates before. These are flat rectangular plates with a bunch of nailing holes and are used to splice to buts ends of framing lumber by spanning the joint and nailing to the two pieces. I've put a few galvanized nails throught some of the holes and set the plate in the cement so half of it is standing up along side where the beam will go. Once the cement is set, place the beam in place and nail to it through the nailer holes.
Peter,
I think I'll keep the stringers on the ground for the additional support.
I hadn't thought of doubling up the stringers. From a strength point of view, does anyone know whether four 4" width stringers evenly spaced apart provide the same support as doubling them up so there are essentially two 8" width stringers?
How would I put rebar in a sonotube--just set a few in vertically?
I think I'll keep the stringers on the ground for the additional support.
I hadn't thought of doubling up the stringers. From a strength point of view, does anyone know whether four 4" width stringers evenly spaced apart provide the same support as doubling them up so there are essentially two 8" width stringers?
How would I put rebar in a sonotube--just set a few in vertically?
gordon
Veteran Member
Usually you would tie the rebar outside the tube then set in in the tube. Have round pieces going horizontal and the straight pieces going vertical. Tied together with tie wire.
As far as the main cross span joists, I would try to place them under where your tractor tires will be going across the bridge. The strongest point. So only two sono tubes at each end of the bridge would be needed. with maybe a cross pour of concrete between the two tubes for added strengh. If you did do a cross pour you would leave rebar coming up out of the top of the tube to tie into the cross pour. Then set your anchors in the cross pour to hook your beams to.
Glenn here is a link to a bridge being built sort of close to what your going to do. http://users.ipa.net/~laniel/Photos/Bridge/
As far as the main cross span joists, I would try to place them under where your tractor tires will be going across the bridge. The strongest point. So only two sono tubes at each end of the bridge would be needed. with maybe a cross pour of concrete between the two tubes for added strengh. If you did do a cross pour you would leave rebar coming up out of the top of the tube to tie into the cross pour. Then set your anchors in the cross pour to hook your beams to.
Glenn here is a link to a bridge being built sort of close to what your going to do. http://users.ipa.net/~laniel/Photos/Bridge/
Anonymous Poster
Epic Contributor
- Joined
- Sep 27, 2005
- Messages
- 29,678
try this site,http://www.fibermesh.com/
fibermesh is easier to use with sonotubes. The fiber is just mixed right in before you pour.
fibermesh is easier to use with sonotubes. The fiber is just mixed right in before you pour.