Rebar tie spacing in uncased drill pier piles

[monpanache]

There is an excellent Thread on ACI 318 - Spacing of Ties however I would like a further opinion. The general rule is that ties must be spaced no greater than 16 times the diameter of the vertical rebar. We are pouring uncased concrete piles (24" O.D. x 20' long) using No. 5 vertical rebar. There are eight vertical rebar tied together in "cages" with No. 3 circular rebar rings. A simple reading of this thread would be that the ties should be spaced at 10". This however is contrary to what we see being done locally where ties are at 12" or more. When I have asked about this the general answer is that the requirements of this part of ACI 318 refer to columns and other vertical supports above ground but not to piles.

I have seen the 16 times vertical rebar diameter requirement on piles made specifically for seismic loads (Zone 2 and above), but this is not the case here, where there is no seismic load. The drilled piers in question are almost all in compressive load only.