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RE: CMU Site Wall using 2001CBC

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The lateral force on the wall should be applied at the center of mass regardless of what 'hx' is taken as to establish 'Fp'. The intent of the equation is to amplify the acceleration for components attached to elevated floors. A cantilevered wall at grade reacts directly to ground acceleration. Thus, 'hx = 0' is what the code "requires". You can of course decide to be more conservative.
 
 
William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com
-----Original Message-----
From: Henry Fairbairn [mailto:hfairbai(--nospam--at)pacbell.net]
Sent: Friday, April 30, 2004 2:22 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: CMU Site Wall using 2001CBC

We just completed a podium structure (concrete basement with retaining walls and slab roof supporting an apartment) and used an amplification factor of 2.5 assuming the hx /hr =0 .5. This would represent the average acceration response of a wall pinned at the top wall. The mass of the wall is lumped at the center. I think for the cantilevered wall hr=hx  A lot of these walls fell over in Northridge, primarily due to lack of reinforcement and inadequate foundations.

"Sherman, William" <ShermanWC(--nospam--at)cdm.com> wrote:
Yes, I would use hx = 0 for a component "attached" at grade.

William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com

> -----Original Message-----
> From: Molly Skinner [mailto:MSkinner(--nospam--at)kpff-irvine.com]
> Sent: Friday, April 30, 2004 11:35 AM
> To: seaint(--nospam--at)seaint.org
> Subject: CMU Site Wall using 2001CBC
>
>
> I am designing a free-standing site wall using the Fp
> equation of section 1632.2. I know the value of ap=1.0 and
> Cp=3.0 per Table 16-O, but what value of hx should be used?
> The code states that hx is the element of component
> attachment elevation with respect to grade, so to me, that
> means that hx should be 0, and as a result the Fp,min
> equation will govern. I've read the blue book, plus looked
> at many books, but this situation never sees to be addressed
> for free-standing (non-building walls). Is using hx=0 appropriate?
>
> Molly Skinner, P.E.
> Irvine, CA