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RE: Soil Pressure

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Thank you for your correction of the terminology.

The geotechs may have a better explanation. What I have is just
a simple analysis in the absence of more complex methods.

The 20 pcf was taken original post regarding soil pressure.

I computed that if soil weight is 150 pcf
for a  sandy soil and if a use a g=.134( not .4 from my previous post)
I get 150x.134 = 20pcf  as additional weight due seismic effects.

Seismic coefficients I  get for a four story RC building
in Zone 4 is about O.12

P = 20 pcf x 8' = 160 psf
for invert. triangle, solving Moment at wall base
M= 1/2x160x8x2/3= 426.6 plf
for rectangular,
M= 160x8x1/2= 640 plf > 426.6 plf

Alex C. Nacionales, C.E.
Iloilo City, Philippines

> -----Original Message-----
> From: Horning, Dick/CVO [mailto:dhorning(--nospam--at)]
> Sent: Thursday, January 28, 1999 12:33 AM
> To: 'seaint(--nospam--at)'
> Subject: RE: Soil Pressure
> The engineering basis for the inverted triangular seismic
> pressure is finite
> element analysis of the soil structure subjected to certain accelerations.
> I'm sure the geotechs in the audience can explain in more detail.  I don't
> see how you can consider a uniform load with resultant lower down the wall
> as "safer".  Also, I don't see how you come up with 20 pcf -
> looks much too
> low compared to the criteria I've seen from geotechs.
> P.S.  Let's be more precise in the terminology - the value in the
> first line
> of your post is the resultant soil *force* per unit length along the wall,
> not pressure.