steel pipe embedded in cored hole in concrete filled with epoxy

[xyyy]

I saw a common practice: core holes (3" dia. example) in concrete, embedded steel pipe (1.5 dia.) in the hole, and then fill the holes with cement type epoxy. My question is how to analyze this kind of pipe anchorage if there is moment, shear, tension forces at the bottom of pipe?
From link

http://www.eng-tips.com/viewthread.cfm?qid=203604,

I can analyze the situation between steel pipe and epoxy. How about between epoxy and concrete. I do not think the concrete surface will be roughened.

Thanks.

 

[KootK]

I'd tackle this in two discrete steps:

1) Use a combination of friction and bearing checks to demonstrate that your post and epoxy assembly engages a blob of concrete.
2) Jury rig some ACI appendix D calculations to demonstrate that the block of concrete will stay put.

If you can provide reinforcing such that step two is unnecessary, all the better. Precasters do something similar with rebar grouted into embedded corrugated sleeves. That's a little more cut and dry though.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[racookpe1978]

What is the epoxy/grout/concrete fill around the steel pipe?

Check your results against Hilti or a competitor to validate your assumptions and calc's. If you know the material of the filler - and IF it is competently installed - then can use that company's calc's from their web page.

 

[Bagman2524]

Shear between the concrete and epoxy caused in tension on the pipe would be resisted by friction between the epoxy and concrete. Seem any tension or pullout of the epoxy from the concrete would have to be caused by bending and would be resisted by adhesion between the concrete and the epoxy. The epoxy manufacturer should be able to provide the adhesion and friction values

"Look for 3 things in a person intelligence, energy and integrity. If they don't have the last one, don't even bother with the first 2. W. Buffet

 

[TXStructural]

I think you will have trouble finding an adhesive that is suitable. You need adhesion to the steel pipe and the cored surface inside the hole. A smooth steel surface is not a good surface for construction anchor adhesives, neither is a cored hole. There is a newer Hilti that says it can be used in oversized holes, but this is excessive. The width of the adhesive layer (3/4" min) will be tough to fill with a good adhesive and achieve the kind of resistance you need. Most bulky adhesives work only moderately well when filling wide gaps between the concrete and anchor, and they rely upon mechanical interlock (hammer drilled holes and threaded/deformed anchors. Your application is not typical.
Repair mortars which are made to fill this kind of hole may not have the adhesion you need, but something like Sika Armatec might help you get bond.

 

[Compositepro]

Epoxy mortar and grouts are heavily filled sand or similar material. Even a little initial adhesion will cause the grout to wedge in the gap between the pipe and hole due to compressive forces in the adhesive generated by the shear.

 

[structSU10]

My firm tends to avoid that detail - especially outside - since we are in a region that has freeze-thaw potential. The mortar around the pipe will allow water in, and when it freezes it cracks the concrete significantly - or if its a curb splits right through it. Just something to think about...

Otherwise, I would try to get an understanding of the fill material - it will probably shrink away from the pipe a bit, more so with a large amount around it, which may limit the pull out resistance. I would think it could handle bending ok - it bears in compression at the top on one face, and compression on the bottom on the opposite face, it just comes down to if the infill mortar can handle the forces.

 

[EngineeringEric]

And do make sure to specify non-shrink non-expanding grout.... not just 'non shrink' unless you want to blow the face off your concrete.