Starting my bridge!!

[EddieWalker]

I'm enjoying the comments from everyone with engineering knowledge. I'm a wood kind of guy, so it's interesting what can be done with metal. I've never seen or used 2x6 metal tubing, but I have bought and used some 2x4 metal tubing with 1/8's thick wall, and in my opinion, that was way too small to support any sort of load over a short distance. I'm struggling to believe that thinner metal, but taller, would be able to support anything spanning 20 feet.

If I was building something to span 20 feet out of wood, I would probably put posts in the ground at two locations to divide the span into thirds, and leave the middle of the creek free to flow. I would also have my beams under the tires for maximum strength. In this design, it appears that the tires will be over the joists, and not on the beams.

I like that concrete will be used to support the bridge. Not knowing the soil there, I would want the depth of the footings to be significant to avoid any settling or erosion from high water when it floods. Is 4 feet enough, or should it be 6 to 8 feet deep? Deeper would be better for the footings to be there 40 years from now. If it's not built to last decades, then why build it?

 

[Doorman63]

Dstig1 had very similar thoughts to mine, he just said it better, mainly in regards to plates at connections and not using rebar. I have seen a lot of rebar handled at construction sites and when guys are carrying long sticks of it it just bows a lot and flops around. In tension that’s fine but in compression it just seems it would buckle easily. Square tubing, round tubing, I beams etc seem to be a better choice. It sounds like you got a lot of scrap a couple of days ago that could be used.

When the install is complete the rebar/rod stock will be in tension

 

[Doorman63]

I'm enjoying the comments from everyone with engineering knowledge. I'm a wood kind of guy, so it's interesting what can be done with metal. I've never seen or used 2x6 metal tubing, but I have bought and used some 2x4 metal tubing with 1/8's thick wall, and in my opinion, that was way too small to support any sort of load over a short distance. I'm struggling to believe that thinner metal, but taller, would be able to support anything spanning 20 feet.

If I was building something to span 20 feet out of wood, I would probably put posts in the ground at two locations to divide the span into thirds, and leave the middle of the creek free to flow. I would also have my beams under the tires for maximum strength. In this design, it appears that the tires will be over the joists, and not on the beams.

I like that concrete will be used to support the bridge. Not knowing the soil there, I would want the depth of the footings to be significant to avoid any settling or erosion from high water when it floods. Is 4 feet enough, or should it be 6 to 8 feet deep? Deeper would be better for the footings to be there 40 years from now. If it's not built to last decades, then why build it?

I’ve got a pile of 2x5 tubes-probably 100 linear feet or more.
The 2x6 I only had 3 this length.

A door manufacturer uses them as a disposable “carriage” for their door assemblies.

The concrete abutments will be set up as a slab with rebar pins going down and some post holes filled with concrete at 2-3 locations.

The creek is a run off ditch from a 50 acre field next to my property. I’ve never seen it up to the top of the banks or see any evidence of it at the location the bridge is.

 

[dodge man]

We already know it will support a couple of atv’s. I personally wouldn’t worry to much about the abutments. It doesn’t sound like an essential bridge. What you have planned will probably work. If you get to carried away your bridge made from “free” material won’t be so free.

 

[Doorman63]

We already know it will support a couple of atv’s. I personally wouldn’t worry to much about the abutments. It doesn’t sound like an essential bridge. What you have planned will probably work. If you get to carried away your bridge made from “free” material won’t be so free.

I’m willing to invest a bit of time/money if I learn something from this.

 

[LD1]

You could certainly truss the top pretty darn good with 100' of 2x5 tube.

 

[Doorman63]

You could certainly truss the top pretty darn good with 100' of 2x5 tube.

You sir……will be the death of me!!!

Those tubes have other uses.

 

[Streetcar]

I’ve got a pile of 2x5 tubes-probably 100 linear feet or more.
The 2x6 I only had 3 this length.

A door manufacturer uses them as a disposable “carriage” for their door assemblies.

The concrete abutments will be set up as a slab with rebar pins going down and some post holes filled with concrete at 2-3 locations.

The creek is a run off ditch from a 50 acre field next to my property. I’ve never seen it up to the top of the banks or see any evidence of it at the location the bridge is.

Rebar pins going into the ground are cost and effort that give you little strength in return. If you want to drive pins use tubing not rods.
The pins will be in compression

 

[LD1]

You sir……will be the death of me!!!

Those tubes have other uses.

Lol.....

I'll try my best. Maybe you should quit mentioning what scraps you have

 

[cfb]

Thank you Doorman for posting. I'll have to look for your barn thread too. I never thought to look at this forum for projects. I'll be looking now. I'd like to see more pix of how the tubes are laid out.
I built a similar size bridge myself. It was one of my most fun projects ever. Hope it is for you too! A couple pix of the finished bridge. I wasn't intending to say so much, but only to encourage others to tackle what might at first seem hard. I built mine of treated wood: mostly 2x6x12's with a few 2x10 x12's. While I wouldn't hesitate to drive a car over it, if I could get it there, my goal was the Ford 8N I'm restoring. I had some free stuff. I salvaged about a 100 bolts which I used to bolt some 2x6's together. I did not bolt all of them, just those used to support the 8N width and my other smaller tractor width. It is sort of like a house floor under the 2x6 planks. I also had two I beams from my garage so those became my support ends on either side of the creek. I sunk 4x4 posts on the inside to hold in the beams which I just laid on a stone foundation. The main span was about 10-11 feet. But I extended both ends to take away the slope. I put one bolt in each of those, not two so that if it needed to rise for the water it would pivot. Only once that I know of did the water go that high. I watched the creek for a few years before this figuring out how high it would go. I used those 4x4 posts too to affix a roof truss to the center of the bridge for added support. I also looked at every bridge I came across while hiking various parks. After all this, I went on-line curious if there was any strength formulas. I guess that should have been my first step. But I was happy that what I did exceeded the expected weight. To relieve my erosion concern, (the bridge is in the middle of a horseshoe) I lined the creek edges with numerous 250 pound blocks that the local recycle shop had for free. But water is powerful. After several washed away, I then pounded rebar stakes through a few fortunate holes in the blocks and then bent over the ends.