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Reinforcement in drilled piers

Reinforcement in drilled piers

Reinforcement in drilled piers

(OP)
I have been requested to design drilled piers that are to support individual columns. The 24' long piers are above grade 4' and below grade 20'.The pier is 24" dia with #6 verts along with #4 ties. My question is how others would look at the min tie spacing and min rho for vertical bars?  I am leaning towards using a 0.5% rho for the vertical bars and 18" c-c spacing max on the ties. Any recommended references or suggestions on this type of application?

RE: Reinforcement in drilled piers

ACI 318 doesn't apply to drilled piers (the part in the ground).  By definition, once you extend out of the ground you are no longer a pier but a column and 318 would apply.

Using the "architectural column" concept for the pier would be fine as long as you assume the smaller column capacity per ACI.  I would simply meet the ACI column tie requirements for the segment above ground (and perhaps 4 feet below grade as well) and let the pier below that simply be designed as a pier.

 

RE: Reinforcement in drilled piers

0.5% for piles and 1.0% for columns (or piers that extend out of the ground). I would keep the 1.0% minimum reinforcing unless the column is really working easily.

RE: Reinforcement in drilled piers

I agree with your 0.5% for rho, but would space the ties at not more than 16*db, in your case, 12" above and below grade.

BA

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