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# RE: Concrete Poles

• To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
• Subject: RE: Concrete Poles
• From: "Cain, William" <bcain(--nospam--at)ebmud.com>
• Date: Tue, 16 Feb 1999 13:10:01 -0800

```My favorite method for drilled piers is one by Czerniak, published in
the Journal of the Structural Division of ASCE in March 1957.  It is
proceedings paper 1188.  The method is limited to caissons for which the
Depth(D) to Diameter(b) ratio is such that deflection within the footing
is not significant (i.e., you assume that the footing is rigid).
Czerniak suggests a maximum D/b ratio of about 10 but given the lack of
precision on the loads and soil resistance in these types of problems,
that D/b ratio is probably a bit conservative.

The method is general in that it can handle various relationships of the
overturning moment and the shear force which allows modeling things such
as rigid pier caps, the caisson being the bottom of a frame or the top
pinned with little additional effort.  Like the Timoshenko beam on an
elastic foundation method Charles Greenlaw referred to for the railing
problem currently being discussed on the listserver, this paper comes
complete with tables, charts and formulas so you can see if it really

Bill Cain, SE
Oakland, CA

-----Original Message-----
From:	Jim Kestner [SMTP:jkestner(--nospam--at)somervilleinc.com]
Sent:	Monday, February 15, 1999 13:34 PM
To:	seaint(--nospam--at)seaint.org
Subject:	Re: Concrete Poles

Mike:

A round concrete pier embedded in the ground is the typical
method used
to support these types of structures. The depth of embedment is
determined by the Rutledge Method. The overturning is resisted
by the
development of opposite passive pressures at different depths
similiar
to a cantilevered sheet pile wall. The biggest unknown will be
conditions. Perhaps you might want to give your client different
embedment depths for different soil conditions.

Jim Kestner, P.E.
Green Bay, Wi.

```