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Re: Seismic mass

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A lot of depends what the Sesimic Design Category is.
RE: NEHRP Provisions Commentary Section 7.5 for Earth Retaining Structures.
RE: NEHRP Provisions Commentary Section page 140 for Slope instability hazard

If you are within the soil block that is moving, I would think that you have to stabilize the whole block + the inertial mass of the structure above. (That is a tall order) If you are not within the soil block, you just have to resist the local forces of the accelerated soil as indicated in the Earth Retaining Structures section.

Harold Sprague

From: Jnapd(--nospam--at)
Reply-To: <seaint(--nospam--at)>
To: seaint(--nospam--at)
Subject: Re: Seismic mass
Date: Tue, 7 Feb 2006 13:55:15 EST

Paul and others:

Another twist to that question..........I have been asked to design a
retaining wall for a house that is in the FEMA flood plane of Riverside County.
The county has a spec sheet they give out.

6'-0" retained height,    8" cmu  #4's @ 16oc at center  of wall,  footing
12" wide 36" deep
4" slab on grade at top of wall,  house sits on top of this.
EFP 30psf;  1500psf soil Bearing;  Passive 250pcf;  soil  115pcf;   solid
grout no inspection.
County claims it is only good 10km from Type B fault)

I cannot get it to calc out as restrained let along cantilevered.

My question is doing a lateral on the project would you do it as two story
and use only the cmu wall weight in the analysis or.........

Do the house calc separately and at as load at top of rigid floor  slab.

Would you at some weight for the dirt in the analysis for the Retained
structure ??

Joe  Venuti
Johnson & Nielsen Associates
Palm Springs,  CA

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