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RE: Drilled piers vs piles

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I think your interpretation of the IBC is correct and you are stuck with the
pile cap requirements of section 1807.2.3 unless you can somehow convince
the Building Official that a grade beam supported on piles is not a pile
cap.

Some ICBO handout notes I obtained at a seminar on the 2000 IBC say that
these new (non-seismic) pile foundation requirements were written based on a
report by the BCMC (Board for Coordination of Model Codes) titled "Pile
Foundation Systems," July 1979. BCMC was a committee of CABO (Council of
American Building Officials) which I think was superceded by the ICC
(International Code Council.)

I had no luck locating a source for this report on the Internet. If you can
find it, there might be some information regarding interpretation that would
help you. If anybody on this list knows where to obtain this, I would be
curious to know a source.

-----Original Message-----
From: Sherman, William [mailto:ShermanWC(--nospam--at)cdm.com]
Sent: Tuesday, March 05, 2002 8:50 AM
To: SeaInt Listserver (E-mail)
Subject: Drilled piers vs piles


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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