Anchor Pull-out for Base Ring

[Ibeam]

I'm having some trouble using ACI 318 Appendix-D for determining embedment length for pull-out.

Situation:
I have an octagonal shaped pedestal/cap, 16'x16', supported by drilled piers. The foundation supports a round vessel, 13'-6" diameter. The moment at the base of the vessel creates tension in some of the bolts. Mserv. = 4700 k-ft. due mostly to WL. DL+Oper.= 231 kip.

Issue 1: The a-bolts are on a bolt-circle pattern, 14'-4" diameter. The least edge distance to center of bolt is 10-inches. What is the best way in determining the Projected concrete failure area(An)for the group?

Issue 2: Per the vessel designers, the a-bolts are 24-each, 2.5-inch dia., F1554 Gr.105. This is a very strong bolt. If I adhere to the ACI code, then I would imagine that the required embedment is greater than 25-inches. In section RD.5.2.2, is this to be interperated that if more than 25" embed, then appendix D doesn't apply?

Issue 3: If the bolt is oversized, which I think it is, is there a minimum pullout capacity to tension force ratio that if you meet; then there's a reduction in the required embedment?

Thanks.

 

[JStephen]

Issue 1- the failure area would be most or maybe all of the pile cap- overlay a big rectangular area as described around the bolts that are in tension. IE, find all bolts that are in tension, go 1.5 x embedment depth in all directions to make the rectangle.

Issue 2- If I remember correctly, App. D is also limited to 2" maximum bolts.

Issue 3- would have to research.

Note that if your design shows inadequate concrete capacity, you can develop the force with reinforcing steel- the commentary is more clear on this than the code.