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[SEAOC] Re: [SEAOC] Re: [SEAOC] Buried or partially buried structure

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        Considering the dynamic effect of earth pressure during an 
        earthquake is common in nuclear and nuclear related designs.

        This subject is explained quite well in ASCE NO. 58,
"Structural 
        Analysis and Design of Nuclear Plant Facilities".  They have
an 
        entire section on seismic effects on soil retaining
structures, 
        buried pipes and conduits which also include design examples.
        
        Thomas Hunt
        TOM.HUNT(--nospam--at)fluordaniel.com


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Subject: [SEAOC] Re: [SEAOC] Buried or partially buried structures
Author:  seaoc::(SEAOCAB) at ~FABRIK
Date:    6/11/96 10:50 AM


From: seaoc(--nospam--at)power.net
Date: Tue, Jun 11, 1996 10:50 AM
Subject: [SEAOC] Re: [SEAOC] Buried or partially buried structures 
To: seaoc
I am also very interested in what other engineers are doing regarding
this 
subject. Latley I have been taking a "poll" when I get the chance to
talk 
to different geotechnical engineers. What I have found is that the
UBC only 
makes a vague reference to required seismic forces due to soil loads
and as 
far as I can tell there is not actual prescribed code load. Seed and 
Whitman(1970) and ATC(1979) addresses this issue and refers to it as
a 
seismic increment. The loads can range from a rectangular
distribution of 
10-40H psf *plus* EFP. I have seen cases where the seismic increment
will 
dominate the wall design. Add traffic surcharge and maybe a wall Fp
and you 
will end up with quite a bunker.
        
Some soils engineers will provide a seismic increment, others will
only 
provide it if requested and some do not beleive it exists. The
seismic 
increment was apparently tested using shake table studies. I have
also 
heard that the seismic increment may not be appropriate for walls
less than 
10 feet unless the walls are finish spaces with very little tolerance
for 
deflection.  I beleive that within the last 5-10 years, it is more
common 
that structures with two to or more story basements, in Zone IV are 
designed using a seismic increment.
        
Do other engineers agree? What do you think?  Any Geotechnical
engineers 
have any comments?
        
        
        
>To All:
>I am wondering what the standard practice is for adding seismic
loads from 
>soil to buried or partially buried structures?  In the past, we have
added 
>such loading when doing DSA and OSHPD work per Title 24.  As far as
I can 
>tell, the new 1994 UBC makes no mention of it.  The 1995 California
Code 
>requires that it be considered if there is more than a 6 foot
differential in 
>soil height on opposite sides of the structure.
>I am looking for some feedback as far as what other Engineers are
doing, or 
>what is "usual and customery" for practicing consulting structural
engineers 
>to do in their designs.
>To be specific (if this will help), we are doing a design of some
man made 
>"wine caves" for a local Santa Barbara winery.  This is an area
where the 
>public will go and taste wine and get tipsy before they go on to the
next 
>winery down the road :)
>Some of the cave is completely buried on both sides, some of it is
buried 
>only on one side, and everything inbetween.  So what do you say, are
we being 
>too conservative if we throw in some soil loading?  It does make a 
>substantail difference in our desgin, and will cost the Owner
significantly 
>more if we do it.  I obviously don't want this thing to come down in
an 
>earthquake, but at the same time, I don't want to spend the Owner's
money 
>needlessly.
>
>Lynn
>
>...
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Regards,
        
Jeff Smith. S.E.
phone: (415) 543-8651
fax: (415) 543-8679
email: smthengr(--nospam--at)sirius.com
        
Smith Engineering
27 South Park
San Francisco, CA 94107
        
...
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Subject: [SEAOC] Re: [SEAOC] Buried or partially buried structures 
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