Rammed aggregate pier uplift calculation scope

[PUEngineer]

We did the structural design of a building where rammed aggregate piers were used to provide a better soil bearing pressure. In addition, at the lateral bracing locations, they were required to provide some uplift resistance.

The rammed aggregate pier submittal came through with notes about the EOR verifying the embedded length of the uplift anchor into the column foundation. This seems like it should fall into the rammed aggregate pier supplier's scope. They set the force in the anchor based on the number of uplift piers used to resist the total force. They set the size of the embed plate in the concrete foundation based on bearing. They set the locations of the uplift piers.

The one calculation they balk at providing is a complete calculation showing the anchor won't pullout of the foundation. Has anyone else experienced this?

 

[OHIOMatt]

Really no different than a PEMB company providing anchor bolts pattern and diameter but not depth. In my opinion, since the anchorage will be based upon the concrete quality and reinforcing it should be up to the eor to ensure that the structure is properly attached to the pier.

 

[ATSE]

PUE,
Which licensee are you dealing with?
The delineation of responsibility is bottom of footing.
You need to communicate to the specialty foundation design-build contactor:
1. Acceptable vertical deflection at factored uplift.
2. Max factored uplift demand at bottom of ftg, stating governing load combo(s).
3. Horizontal control and tolerance for individual threaded rods, and for rod group (this is usually 3"); this is to ensure that the footing and the RAP group is primarily concentric.
4. Minimum design life (say 50-75years) considering corrosion, and any sacrificial thickness (usually 1/8" on the diameter).

Depth of Rammed Aggregate Pier and depth of deadman plate at bottom of pier (or sometimes higher) is a RAP designer's responsiblity, just as you have suggested.

Your responsibility is to confirm proper anchorage and deflection compatibility.

 

[PUEngineer]

OHIO

I sort of see that analogy. The original analogy that came to my mind is the stair supplier asking me to verify the embedment depth of their epoxy or expansion anchors. I guess where the PEMB analogy gets confusing is that as the foundation designer, that's clearly part of your responsibility and happens during that phase of the project, not on the back-end when shop drawings come through.

ATSE

I think the majority of that was covered in the specifications. I still don't understand how it's the EOR's responsibility to verify the proper anchorage when all the variables are set by the RAP designer. Sure, we could do it, but it doesn't make sense to me.

 

[ATSE]

Clarification
Your responsibility is to confirm proper anchorage IN THE CONCRETE FOUNDATION (not below grade) and deflection compatibility OF THE STRUCTURAL SYSTEM (and insure the RAP deflection is not excessive).
That is, you and I agree.