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FW: Perforate shear wall design and combined shear and uplift on edge

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In general, if the uplift to which you are referring is a result of the
shear loads only, then the perforated shear wall design method takes
that into account by reducing the shear capacity of the wall.  The shear
capacity is reduced because the bottom plate nails are resisting both
shear and uplift (from overturning only).

If the uplift you are referring to is a result of vertical accelerations
or wind uplift, then the shear capacity of the shear wall must be
further reduced and uplift around window and door openings must be
resisted by connectors.  

I think there may be some confusion because the APA paper on resisting
combined shear and uplift is for wind (Tom Skaggs can correct me if I'm
wrong on that point).

Hope this helps.

Buddy

John "Buddy" Showalter, P.E. 
Director, Technical Media 
AF&PA/American Wood Council 
1111 19th Street, NW, Suite 800 
Washington, DC 20036 
P: 202-463-2769 
F: 202-463-2791 
http://www.awc.org 

The American Wood Council (AWC) is the wood products division of the
American Forest & Paper Association (AF&PA). AWC develops
internationally recognized standards for wood design and construction.
Its efforts with building codes and standards, engineering and research,
and technology transfer ensure proper application for engineered and
traditional wood products.

********************* 
The guidance provided herein is not a formal interpretation of any AF&PA
standard.  Interpretations of AF&PA standards are only available through
a formal process outlined in AF&PA's standards development procedures.

********************* 

> 
> From: "Alexander (Sasha) Itsekson" <sasha(--nospam--at)enginious-structures.com>
> To: "seaint(--nospam--at)seaint.org" <seaint(--nospam--at)seaint.org>
> Subject: Perforate shear wall design and combined shear and
> uplift on edge
> 
> Hi list,
> I am working on a retrofit of an existing apartment building
> built around 1= 970's. It has existing plywood shear walls on 
> the exterior and a few inter= ior shear walls with no 
> holdowns and plywood lapped over the rim block/jois= t for 
> shear transfer at the exterior. As was customary at the time, 
> it has= a soft story that we are proposing to retrofit.
> 
> I am trying to determine how much uplift/overturning can the
> existing shear= walls above deliver to the structure at the 
> soft story level. It would be= way too conservative in my 
> opinion that it can transfer the forces as per = my design 
> criteria and even based on the shear wall capacity because of 
> the= lack of holdowns. That is why I started looking at the 
> perforated shear w= all design procedure new to the IBC 2006 
> and also reviewing an APA technica= l note H335 "Structural 
> Panel sheathing or siding used to resist combined s= hear and uplift".
> 
> The essence of what I am looking for is how much shear and
> uplift can a wal= l nailed to a rim joist transfer (as the 
> worst case scenario). The APA doc= ument says that " wind 
> uplift loads occurring at windows or door headers, e= ven in 
> perforated shear wall, must be distributed around the 
> openings and i= nto the structure below by the way of 
> hardware specifically designed for su= ch application". In my 
> case these opening are existing and there is no hard= ware 
> except for a few toe nails. Here's the question: does that 
> statement also applies to horizontal seismic= loads? I think 
> that this requirement has to do with the uplift from the r= 
> oof structure above and it is not applicable to the seismic 
> loads. Are the= re any references about that? (Buddy 
> Showalter are you reading this?) If = I am right, then one 
> can assess both shear and uplift capacity of the plywo= od 
> shear wall without any holdowns or other hardware around the 
> window open= ings.
> 
> Another question is somewhat unrelated to my situation but is
> regarding the= general application of the Perforated shear 
> wall method: If one has to at= tach each stud with strap to 
> the structure below for the unit uplift force = equal to the 
> shear unit force, is that a viable method of designing and 
> con= structing shear walls. My first reaction is that it 
> would be cheaper and e= asier to strap and block around 
> window and door openings while still provid= ing for uplift 
> hardware at the ends of the entire shear wall.
> 
> Regards,
> 
> Sasha Itsekson, SE
> Enginious Structures, Inc.
> Oakland, CA
> 

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