Design of Anchors for Concrete & Steel Post Embedment in concrete

CJ...are you looking for cast-in-place anchors or post-installed anchors? It makes a difference.

Embedding a 50mm steel pole in concrete will require that you compute the shear break-out from lateral loading or an equivalent couple if there is a moment resistance required.

See AISC design guide one for CIP anchors and ACI 318 appendix D for post installed anchors. I'd love to see an example for the embedded pole too.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

Third vote for an embedded post method.

For post installed anchors you're better off using tested anchors. Hilt for example. I've never had much luck getting app d to work out reasonably.

If you embed the pole, it will rust if not galvanized or stainless. The expanding rust will likely spall the concrete if you are too close to the edge.

… unless it it used in a dry environment

for the steel pole, are you talking about like a handrail post?

Yes a handrail post would be a typical example. So I'm a bit unsure how to analyse this with respect to sufficient cover for the shear loading and moment resistance.

Have I posted this in the right section of the forum?

cj...see attached. Maybe it will help....

There's a method for calculating the strength of a steel shape embedded in concrete in the canadian precast manual. I'll grab it tomorrow if I remember.

Anybody come up with a solution for the steel pipe embedded in concrete?

Steel pipe (solid round, hollow pole, or thin round rod or hollow member) in concrete:

Three failure modes - and a few more related-failures mentioned above such as rust in the metal, thus inducing a failure by the metal loss causing a wall failure. All of the rod-in-concrete failures assume no "force bends the rod" type failure as well.

Imagine a vertical rod or anchor near the edge of a concrete sidewalk or a concrete deck above grade, with the vertical steel (round) rod being forced either sideways at the top, or being pulled up from the top, or some combination of the two. In almost all cases, the vertical rod is set into a drilled 9or cored) hole in the concrete, then the hole is filled with mortar, grout, epoxy, or a two-part filler. An anchor bolt for example, is drilled into a tightly fitting hole, then the epoxy goes between the tight hole and the outer poured slab. A 1-1/4 handrail post on the edge of a sidewalk has a 3 inch hole cored-drilled into the sidewalk, then the grout or concrete mortar is poured in the 3 inch hole and allowed to set.

The base as a whole (concrete around the rod and material around the concrete) is stiff enough, but the rod bends or pulls out of the base and material. (There is not enough resistance between the metal and the concrete, so the anchor bolt pulls out. The handrail is pulled up when the concrete walk settles.

The rod is stiff enough, but the filler around the rod fails (cracks). (The filler material yields, but the sidewalk or slab remains whole.)

The rod is stiff enough, and the concrete filler around the rod is stiff enough, but the material surrounding the concrete fails (yields to the prying and tearing force). The 2 inch dia vertical post is set in a 6 inch dia concrete "posthole" but the dirt around the posthole fails, and the post and posthole concrete falls over. The dirt below a deck post slides downhill, and the entire deck goes down because the soil moved. A handrail is pushed over because the thin concrete between the the edge of the sidewalk cracked away when somebody sits on the handrail.

The rod and concrete around the rod is strong enough, but the concrete slug pulls out or pulls through the larger hole.


These cases never seem to be addressed. Just the basic 50 lbf (US) per foot of rail, or 200 lbf point load is written.

Seems like there would be a test case somewhere publicized where the thumb rules are verified: A 3 inch diameter hole around a 1-1/4 dia pipe filled with 3000 psi grout core-drilled into a 4 inch sidewalk breaks at 256 lbf sides force at 42 inches height if the center of the core is 4 inches from the edge of the sidewalk.

The above test assembly breaks at 310 lbf sideways force in a 6 inch thick poured concrete sidewalk.

The above test assembly breaks at 150 lbf in a 2 inch thick slab.

A 3 inch grouted dia hole around a 1-1/4 dia pipe 42 inches tall breaks at 150 lbf sideways force if the grouted hole is 2 inches from the edge of a 4 inch sidewalk. Etc.

The anchor bolt web sites have pull-out factors and margins for their anchor-and-epoxy combinations, and have reduction factors for holes drilled closer to an open side than a 45 degree cone from the bottom of the drilled hole, but I've never seen cases analyzing the sidewalk (or a deck concrete) surrounding a cored-drilled posthole being tested for ultimate failures.

There's a method for calculating the strength of a steel shape embedded in concrete in the canadian precast manual. I'll grab it tomorrow if I remember.

Anybody have this book or the relevant extracts or similar code with examples?

The Canadian Precast Manual has the method shown below. It doesn't have much to say about breakout capacity etc at edge conditions however.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

Foundation and Anchor Design Guide for Metal Buildings has some great examples, and if you ever do PEMB foundations it has some great resources:


Also, TEKLA Tedds and RISA Base both are good programs. I use an excel spreadsheet too as a double check.

Lastly, for post-installed anchors I use Profis by Hilti. It's intuitive and easy to use. And Hilti anchors are the best IMHO.