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# RE: Use of Side Friction to Resist Overturning - Spread Footing

• To: SEAINT(--nospam--at)seaint.org
• Subject: RE: Use of Side Friction to Resist Overturning - Spread Footing
• From: "Benson,Ralph" <rbenson(--nospam--at)huitt-zollars.com>
• Date: Tue, 15 Dec 1998 8:56 -0600

```I have used side cohesion to resist lateral loads and overturning moments
on large (30'x15'
embedded 10 to 20' into the soil with vertical and lateral loads in the
150k range). )
guy wire anchors cast directly against clean, unbroken rock.  The
cohesion values
used were similar to 500 psf and were determined by a geotechnical
engineer
(not assumed).  The side resistance values were neglected for the top two
feet of the anchors,
as directed by the geotech.

If you follow this approach (and my math holds), you get 3.0k of
resistance
at 1.5 foot above the bottom of the footing, resulting in 4.5 ft-k of
moment resistance.
Which, I would guess, might be small compared to the required resistance.

What does the geotechnical report recommend or is there one?

-----Original Message-----
From: Robert Rogers [SMTP:robert.rogers(--nospam--at)woolpert.com]
Sent: Tuesday, December 15, 1998 6:10 AM
To: SEAINT
Subject: Use of Side Friction to Resist Overturning - Spread Footing

I have recently seen a set of calculations for the design of reinforced
concrete spread footings (for a new building) which support building
footings
are approximately 5 ft. deep (to bottom of footing), 2 ft. thick, and
have
a 3' tall square pier which receives the square column.  The
calculations
assume a value of 500 psf for side friction on the 2' thick footing.
The
forces generated by this side friction are supposed to help resist the
overturning moment imposed to the footing.  I have never seen this type
of
analysis used for spread footing design.  I think the methodology is way

out in left field !  Any other opinions ?

```