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Re: 3/8" Plywood shear values on metal studs.

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My experience of performing hundreds of cyclic shear wall tests  (per
SEAOSC Panel Test Metod) has lead me to the concusion that 3/8 ply on wood
studs at 16" oc is not a bad system. The real problem is from mixed
systems (pywood/stucco/drywall)
and from unrealistically high ductilities for plywood systems.  We
recently presented on paper comparing the SEAOSC method with two similar
but modified test sequences at EERI Conference (June 98).  Sample ultimate
stength was a function of test sequence (more cycles yielded lower
strength).  Sample displacement (disp at SLS) was nearly independent of
test sequence;  they all gave up at approx 2% drift.  So unless you can
assure yourselves that the actual shearwall drifts will be less than 2% in
an e/q. I highly suggest that you get copies of recent APA Report on
shearwalls they  support the drift finding.  

The key to building survival is drift contro.  Which requires some type of
dynamic (even if simplified) analysis.  Dynamic analysis requires stregth
AND stiffness data.  This type of information is being developed by APA
and others.  We are currently begining a 60 panel test program and over
the next 24 months will be adding to the knowledge base.    

How does all this relate to 3/8 ply  on steel studs?  We have not tested
3/8 ply on steel studes but have tested OSB & drywall on steel .
Fastener
is critcal; some screws tend to be more brittle than nails.  Fasteners 
in steel studs behave very differently than ones in wood studs.  Hopefully
we will soon have difinitive answeers to these types of questions.

Arbitrary prescriptive H:W ratios and "when in doubt make it stout"
attitudes are no substitute for test data, sound engineering judgement
and proper analysis.

 regards
Robert Kazanjy, PE   ***DISCLAIMER*** I speak for myself not UC-Irvine
Senior Development Engineer
Dept of Civil & Environ Eng
UC - Irvine
  
On Sun, 12 Jul 1998 Rhkratzse(--nospam--at)aol.com wrote:

> 
> In a message dated 7/11/98 3:28:45 PM, Tom B. wrote:
> 
> <<3/8" would give one the hebee gebees after Northridge.  Let's all
> design the walls according to their relative flexural and shear rigidities and
> limit the H:W to reasonable values as well.  This, along with 15/32" five ply
> struct.I and 10d commons should solve the problem>>
> 
> I assume you're talking about total rigidity (including both flexural and
> shear deflections).  And what would you consider a "reasonable value" of H:W,
> and would it vary in different situations? 
> 
> Ralph Hueston Kratz, S.E.
> Richmond CA
> 
> 
>