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Rebar cattle guard plans

Looking for a cattle guard that can be made from available supplies at local home depot. Needs to be able to support 32,000 lbs to meet HS-20 aka cement truck.

Schedule 40 re-bar has a tensile strength 60,000 pounds.

Anybody got any bright ideas as to how to improve this plan? Or does it look like it will hold up?

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The catch is that tensile strength isn't what you need. You need flexural strength, of which rebar has very little. That said, HD does sell steep pipe, which would have much higher flexural strength pound-for-pound. –  DA01 Mar 13 at 18:31
    
Have you seen these cattle guard forms? cattleguardforms.com Maybe you could get those or build your own forms with rebar and high strength concrete? This pdf from the forestry service may also be useful. fs.fed.us/eng/pubs/pdfpubs/pdf98232826/pdf98232826pt03.pdf –  OrganicLawnDIY Mar 14 at 0:23
    
Not gonna happen with Rebar. Rebar is soft, tough and has little strength against bending. In other words, you're mistaking pulling the rod in half for bending it in half. Its strength is in tension. If you go examine cattle guards, you will find they're made of steel that is formed into channel elemements and has sufficient hardness (carbon content which rebar iron lacks) to be springy. Buy a cattle guard rated for the load, it's going to be kind of expensive making one out of the hot rolled steel channel you need to handle 16 tons rolling over it. –  Fiasco Labs Mar 14 at 1:52
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A local construction site uses thick 3" angle iron at their truck entrance (laid so the corner of the angle iron is pointed upwards). I think this is to let the mud fall off their tires since we have no cattle but should work as a cattle guard. –  Johnny Mar 14 at 14:53
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2 Answers 2

No way in heck that will hold up a concrete truck.

If it "Must come from Home Depot", see if they have any 12 foot 3" lally columns - the solid concrete filled ones, not the adjustable ones. Or see what they have for big iron pipe. Those should probably still have supports at the third points (or more) - down to the bottom of the pit, not across it.

If you have cattle that know about cattle guards, then you can also get away with painting parallel black & white stripes on the road, according to several sources. Looks like one so they treat it like one, is the claim. Sure worth a try.

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IMO the painted stripes are more like a deterrent than an actual barrier. It's probably more effective on busier roads where cattle are less likely to hang out on the roadway. I've seen cattle stumble across a real cattle guard when standing next to the guard, then getting spooked by an oncoming vehicle. If it were just paint, the whole group would be across instead of a couple individuals. Then the gig would be up. They may be fairly stupid, but they do learn. –  bcworkz Mar 13 at 17:31
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With a 6 foot span, you'll need to look up the bending strength of the I-beam to be used. You're in reality, building a short span bridge. And for this reason also, concrete trucks are allowed a maximum of 38,000 per axle which kind of explains those huge flotation tires they use on the front axle.

I-beam to bridge the gap, three sections under each tread area where the duals will roll and two more equidistant between them and two on the outside.

Overlay with 1 1/4 rebar for the cross-road decking, welded in place so it won't roll.

Here's what the construction of a 32,000 lb. per axle rated cattle guard is going to look like:

enter image description here

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Note that the rectangular tubing used in the photo will have far more bending stiffness than solid round rebar (per unit weight...1 1/4 rebar may get the job done, but that sucker is gonna be HEAVY and expensive, better to use appropriate tubing) –  mac Mar 14 at 20:14
    
Ayep on that, the steel tubing is going to be stiffer than iron rebar and have a lot more efficient use of the materials. For supporting a cement truck, it's going to be expensive any way you look at it, a 12' H-20 will cost in the $3000 range as long as they do light loads on the cement truck which would call for an H-25 and another $1000 if you're fully loaded. –  Fiasco Labs Mar 15 at 1:43
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