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RE: Sliding

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As a plan reviewer I saw  alot of people say they were using the slab on grade to transmit lateral force into the soil or to other gravity footings, but they forgot to calc it out and detail it.  There is more to the design than just checking concrete bearing at the end of a wall or pedestal which is a dubious mechanism at best. 
 
Most S.O.G. have isolation joints at structural elements and  get cut up for plumbing repairs etc....  Also what kind of a friction coefficient is there between concrete-visquene-soil or a sand bed, visquene and soil.  Using a S.O.G. is not a magic cure to take out shear wall and braced frame footing reactions and requires some design.
-----Original Message-----
From: Paul Crocker [mailto:paulc(--nospam--at)ckcps.com]
Sent: Thursday, November 14, 2002 1:27 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Sliding

    I recently asked a geotechnical engineer on a project about the possibility of having soil friction along the sides of the wall footing, due both to cohesion (like a pile) and friction resulting from the soil pressure on the sides of the footing.  He told me that such forces do exist, but that they aren't particularly significant.  That will probably depend on your soil and the willingness of your geotech to look into it, since it isn't typically considered.  
    Another approach you can try is to reinforce the slab on grade (if you have one) and use that to spread the sliding force to other parts of the building.  The detailing could be tricky, though, depending on how things are laid out.  You can also look at tie beams that extend out to adjacent columns in line with the wall.  There are quite a few variations and combinations of those concepts. 
   
Paul Crocker, P.E.
 
-----Original Message-----
From: RDAHLMANN(--nospam--at)aol.com [mailto:RDAHLMANN(--nospam--at)aol.com]
Sent: Wednesday, November 13, 2002 6:40 PM
To: seaint(--nospam--at)seaint.org
Subject: Sliding

I have a question about sliding in long shear walls. In high seismic regions, sliding can govern footing sizes. Resistance is provided by the friction factor times the dead load weight (times appropriate factors) plus any passive pressure. This can also include return walls.

For long shear walls, it seems like there should be some sort of side friction factor also (similar to caisson skin friction). I have not seen this anywhere, but I would like some input about this possibility.

Thanks
Richard Dahlmann, P.E.
Phoenix