Bracing fence corners with T-posts

[quicksandfarmer]

I do something similar, but I'm using 6inch x 8foot treated wood posts in concrete with 1 1/2 inch EMT for my bracing that is also set in concrete and attached with a 5 inch exterior structural screw.

The EMT comes in 10 foot lengths. I cut them in half at 45 degrees, drill a hole through the angle part of the EMT for the structural screw and anchor the other end in concrete.

I always bring the concrete up the post so water sheds away from it. In my experience, posts always rot at ground level, so keeping the water away from the base of the post will keep them from rotting.

My fencing is 4ft 2x4 horse fence. I like the wood posts because I can attach the fence to the posts with barbed staples, that make it very secure.

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Thanks Eddie.
I assume you went through the same thought process I did, of walking around Lowes and Home Depot and deciding that EMT was the cheapest way to buy long pieces of steel tubing.

I was hoping this thread would catch more attention than it has. What really amazed me was how strong a brace that is only supported at the bottom with a T-post, a piece of 2x4 and a piece of PVC pipe is. Probably not as strong as buried in concrete, but you can put them up and take them down in a few minutes with hand tools. I've never tested the ultimate pull out strength, I don't want to ruin a good section of fence. But I once did four strands of electric and tensioned each strand to 100 lbs on a scale and the corner didn't budge.

 

[EddieWalker]

Yes, I bet we did the exact same thing!!

Did you also look at H bracing at other farms and wonder how to make it stronger, and then realized that all the strength was from the diagonal bracing? and the extra post wasn't needed? Just one post and diagonal bracing was all that's needed for the same results.

 

[Torvy]

I'm in the process of having perimeter fence installed. Was going to DIY, but SWMBO decided she wasn't down for that level of work and chose to spend money instead.

Field fence with a strand of barbed wire above and below.

I guess I'm old-school. I prefer the wood braces.

 

[quicksandfarmer]

Yes, I bet we did the exact same thing!!

Did you also look at H bracing at other farms and wonder how to make it stronger, and then realized that all the strength was from the diagonal bracing? and the extra post wasn't needed? Just one post and diagonal bracing was all that's needed for the same results.

The first thing I did was sketch up a force diagram.

If you have a fence post with a 10' brace attached 4' from the ground, subject to a 100 lb horizontal force either centered on the post or evenly distributed, what are the forces?

Well, since the horizontal load is centered half goes on the brace and half on the ground under the post. That horizontal load is transferred to the ground under the brace. Since the brace is angled there will be a vertical load on the brace of 21.8 lb. This will push down on the bottom of the brace and up on the post.

So what are the failure modes of a brace like this? Whichever of the following happens first:
* The post pulls sideways -- the horizontal force exceeds holding capacity of the earth.
* The anchor of the brace pulls sideways -- again, excessive horizontal force.
* The post lifts up out of the ground -- the vertical force exceeds the holding capacity of the earth.
* The anchor of the brace sinks into the ground
* The post or the brace bends or cracks.

I don't make it a habit to go around breaking braced corners, so I have limited experience. Usually when I do break a corner it's installing field fence with a come-along and I get too enthusiastic tightening.

With an H-brace made out of wood timbers, I find the failure point will be when the post lifts out of the ground -- the holding capacity of the earth gets exceeded. This depends on how you anchor your posts, I usually just pack them in dirt.

With a T-post on the corner, the post itself bends before anything pulls out of the ground. That really surprised me.


If you go back to post #4, I show a picture of a wooden post with the braces anchored with t-posts. I've never broken one of those braces so I don't know if the post pulls out before the braces let loose of the earth. Or if something else gives.

 

[QRTRHRS]

I got brackets at Tractor Supply that hold aT-post that are screwed into a wooden post. I used them for a post that I was not able to get into the ground far enough due to solid rock. I braced the bottom of the T-post's with large flat rocks then screwed in the brackets. Been holding up for seven years.