Need a book? Engineering books recommendations...

# RE: Uplift on Belled Drilled Pier

• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: Uplift on Belled Drilled Pier
• From: "brkoch" <brkoch(--nospam--at)pacbell.net>
• Date: Thu, 13 Nov 2003 09:22:38 -0800

```Rich,

Within Bowles' Foundation Analysis and Design this subject is discussed
in sections 16-13 and 4-11.

>From Section 16-13:  "The pullout resistance can be estimated using the
shaft skin resistance + the pile weight and the method of Sec 4-11. If
the soil is reasonably competent and the base enlargement is on the
order of 2D, the pullout capacity of the pile should be about 2x the
shaft skin resistance plus pile weight."

Equations are presented in section 4-11 which are NOT based the
truncated quasi-conical soil pull out zone observed in model and full
scale testing. The equations do include the effects of the footing and
soil weight as well as passive pressure friction resistance on a
cylindrical surface defined by the diameter of the footing (or bell
internal friction. The equations estimate an ultimate capacity and
should be reduced by an appropriate factor of safety.

Sincerely,
Brent

Brent R. Koch, P.E.
Koch Engineering, Inc.
Livermore, CA
tel:(925)456-7164
fax:(925)456-7163
brent(--nospam--at)kochengineering.net

-----Original Message-----
From: richard lewis [mailto:rlewistx(--nospam--at)juno.com]
Sent: Thursday, November 13, 2003 08:18 AM
To: seaint(--nospam--at)seaint.org
Subject: Uplift on Belled Drilled Pier

I am working on a drilled pier foundation for a pre-engineered metal
building.  There are significant uplift loads on the frames.  I will be
belling the bearing ends of the piers.  For uplift resistance I know I
can use skin friction.  But for the bell contribution, how is uplift
resistance calculated?  Is it the weight of a soil wedge based on the
angle of friction?

Thanks.

Rich

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted