A way to strengthen metal fenceposts?

Hello, I was given a suggestion the other day that I wondered if someone out there could confirm or deny. It was about a way to strengthen metal fenceposts.

It's common here (DFW area) to use the 2 3/8" metal posts when erecting a wood fence. Sometimes, however, a fence will give way during a severe enough storm. When it does, the metal posts always seem to bend or break off at right about ground level.

A fellow who seems to have had quite a bit of experience doing fences suggested a way to offset that. He said that filling the interior of the posts themselves up past ground level with concrete would help keep that from happening. I have to admit that the idea makes pretty good sense.

Any experiences with this, true or false?

 

True. This technique is commonly used with pipe bollards. Bollards (heavy duty "posts") protect such things as building corners, electrical equipment, and fire hydrants, near parking areas.

A rigidly fixed post under load "bends". One side is under compression(foreshortens); the other under tension (elongates). In a solid post the neutral axis (point where the two forces are equal) is in the center of the post.

Given the greater stress is exerted on the outer portions of the post, thickening the post wall increases bending resistance. Changing the shape from round to square, or from round to an I beam, increases bending resistance. Solidifying a tube increases bending resistance. Filling with concrete is not as effective as increasing wall thickness or changing the shape, but it's a proven technique.

 

Thanks for the info! I'm in the process of replacing a decaying wood fence. I think this is worth a try, especially since concrete is not too expensive.

 

Fill your posts with the bag mix concrete you get from a home center instead of using ready mix (from a concrete truck). Most bag mixes use small, rounded river rock where ready mixed concrete uses larger stones that are jagged. The bag mix concrete is easier to get to flow down inside a small pipe.

Buy a large funnel and cut the tip off to make the hole as large as possible to help get the concrete into the pipe. You can also make a funnel out of some metal flashing by curling it into a cone shape and duct tape it in place.

Vibrate the post by tapping on it with a hammer when you are filling it. This will help the concrete slide/settle all the way to the bottom and helps to work out air bubbles.