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Re: Hold downs with "Perforated Shear Wall Method" and "Force Transfer Method"

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By 2305.3.8.2.3, it looks like you don't have to always use equation
23-3 that is under 2305.3.8.2.4 if using "principles of mechanics".

"Anchorage and load path. Design of
perforated shear wall anchorage and load path shall
conform to the requirements of Sections 2305.3.8.2.4
through 2305.3.8.2.8, or shall be calculated using
principles of mechanics."

WH

On Fri, May 23, 2008 at 10:00 AM, Scott Maxwell <smaxwell(--nospam--at)umich.edu> wrote:
> I think I understand the intent of what you are saying, but wording does
> bother me.
>
> With wind or seismic in one direction so that the shearwall is not loaded,
> but there is overall uplift on that wall, there would be no possible
> "double-dipping" as the wall would not be subjected to overturning (assuming
> a simple diaphragm, thus no torsional effects).
>
> With the wind or seismic in the other direction, the wall (if a shearwall)
> should be exposed to both overturning and potentially net uplift (due to
> wind uplift or the vertical component of a seismic force...overall, more
> logical to think about it in terms of net wind uplift) AT THE SAME TIME.
> Thus, the same dead load should be resisting both the uplift AND the
> overturning.  In other words, your FBD of the shearwall will have the wind
> overturning force, the net uplift, and the 60% of the dead load that would
> work to resist both...all as loads applied to the shearwall.  I don't
> consider that "double-dipping".  I agree that if, for some reason, you check
> the wall seperately for uplift and for overturning, then the same dead load
> should not be used in both check...but I would think you should be checking
> both uplift and overturning in the same check.
>
> Am I missing something?
>
> Regards,
>
> Scott
> Adrian, MI
>
> -----Original Message-----
> From: Showalter, Buddy [mailto:Buddy_Showalter(--nospam--at)afandpa.org] On Behalf Of AWC
> Info
> Sent: Friday, May 23, 2008 9:47 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Hold downs with "Perforated Shear Wall Method" and "Force
> Transfer Method"
>
>
> One caveat however, the WFCM does not use dead load to offset uplift and use
> the same dead load again to offset overturning (double-dipping). So in the
> WFCM tables, we only show dead load offsetting uplift loads.
>
>
>
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