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Drilled piers vs piles

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Question regarding 2000 IBC vs 1997 UBC requirements for drilled
piers/piles:

I have a design using 24" diameter cast-in-place concrete drilled piers for
a depth of 50 ft. The piers support a structure on a grid of grade beams
which support structural slabs and masonry walls. The tops of the drilled
piers are flush with the bottom of the grade beams, with dowels projecting
from the pier into the grade beam. The project is in a low seismic region.
Drilled pier design is in accordance with a site geotechnical report. The
original design was performed under the 1997 UBC. The local jurisdiction has
now adopted the 2000 IBC and the design must be brought into conformance
with the IBC.

According to IBC 1807.1 definitions, this "drilled pier" is defined as a
"caisson pile" due to its length to diameter ratio. According to IBC
1807.2.3, piles must be embedded 3" into "pile caps" with at least 4"
concrete cover beyond the edges of piles. It is not clear to me what the
intent is in this section - does this only apply to pile caps which connect
a localized group of piles or does it also apply to grade beams sitting on
top of piles? Do all "piles" require pile caps? (To meet this requirement, I
would need to significantly widen my grade beams, as well as deepen them, to
accomplish the side cover and embedment requirements.)

Any thoughts on the code's intent here would be helpful.


William C. Sherman, PE
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com

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