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RE: UBC CODE INTERPRETATION

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You should include seismic acceleration on the foundation when checking
sliding of the overall structure (i.e., sliding force = 7.25 kip per your
example). The earthquake motions are imparted to the structure at the bottom
of the foundation (via friction). The inertia of the foundation will try to
resist lateral movement, i.e. it doesn't know how to interpret the code, it
just reacts to acceleration (F=Ma). 

> -----Original Message-----
> From: Vinod Sahni [mailto:SAHNIVK(--nospam--at)nv.doe.gov]
> Sent: Wednesday, December 06, 2000 9:29 AM
> To: JLUTZ(--nospam--at)earthtech.com; seaint(--nospam--at)seaint.org
> Subject: Ref: UBC CODE INTERPRETATION
> 
> 
> Thanks for your reply. 
> But I probably got misunderstood or I did not clarify my 
> question enough.
> 
> Basically, the question is this:
> 
> Let us assume the following - 
> 
> Equipment Wt = 5 kip,  Accel at CG of Equipment = 0.65g
> Foundation Wt = 10 kips, Max Ground Accel = 0.40g
> 
> Let us calculate base shear for foundation sliding check:
> 
> Sliding Force = 5 kip x 0.65 = 3.25 kip ( I believe this will 
> meet code).
> 
> OR, 
> 
> Force = 5 kip x 0.65  +  10 kip x 0.40  =  7.25 kip (I do not 
> think code
> requires this method).
> 
> I would appreciate your looking into this further and giving 
> your opinion.
> 
> Thanks again.
> 
>