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# Re: Uplift on Belled Drilled Pier

• To: <seaint(--nospam--at)seaint.org>
• Subject: Re: Uplift on Belled Drilled Pier
• From: "DA" <dnae(--nospam--at)cox.net>
• Date: Thu, 13 Nov 2003 10:19:13 -0800

```
Rich
If you are doing piles that is means you soil engineer and soil report
the soil engineer should give you the value of uplift
the skin friction it reduced to half value for uplift
the belled potion of the pile it should not considered because it might fail
unless you reinforced , and the way I would do it is to calculate the weight
of soil
carried by belled portion that is means the difference of area of pile and
belled portion
multiply by the depth of pile
I  hope that help
Dave A P.E..

----- Original Message -----
From: "brkoch" <brkoch(--nospam--at)pacbell.net>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, November 13, 2003 9:22 AM
Subject: RE: Uplift on Belled Drilled Pier

> 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
> diameter in your case) with additional factoring based on shape and
> 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
>
>
>
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