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Fwd: Re: Calc-out versus reality: modeling & research: for Sam Love et al

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Hi I'm new here and clumsy on the keyboard but an old timer in the SE (&
arch) scene. Pls forgive wordiness and typos.  My motives are pure.  <:>
Re wood shear walls: we need full scale reversing dynamic testing run by
actual designers.  Check w/ UC Forest Prod Lab, Ed Diekmann, Ed Zacher, even
me.

What follows is personal opinion, but it's based on full scale dynamic tests
back in 85 by Ed Z and me (see 85 SEAOC Proceedings, Architecture, ASCE 12th
World Congress Proceedings).  They were great fun and showed a lot of things.

First, our current accepted and anointed practice.  This model has been
around for 40+ years and nobody's happy w/ it. It's related to aircraft
design, semi-monococque, tension field or whatever you want to call it.  The
plywood is supposed to act in pure shear and the plates and studs and rim
joists and so on take the flex couple.

It requires you to take sections along the edges of the holes and across the
wall (or floor or roof) to get unit shear flow in each panel and then take
sections along edges of collectors (=drag struts) and apply unit shears found
from the panels.  Studs at hole edges may show a net residual tension at the
bottom: there's your tie-down force.

BUT IT DOESN"T REALLY WORK THAT WAY.  How about that?

In reality each piece of PW moves as a rigid body, translating and rotating
trying to follow the parallelogram of the deflected plates & studs (or
joists) with the nails bridging the incompatibility and the edges fouling.
 If you use nice common (ductile) nails, not grabbers or screws or other
kinds of cold-worked connectors, the system is ductile at least until the
nails get strain hardened.  The significant action is in the energy
dissipation of the nails and also the edges rubbing and so on.  

Ed D has full-scale test evidence that it's the number of nails in flexure
that counts.  I like that.

In any case, don't depend on top or sole plate bending for anything.  The
plumber has been at it with his chain saw for sure.

Good luck to us all.

Gary




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Subject: Re: Calc-out versus reality: modeling & research: for Sam Love et al
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Richard Lewis, P.E.
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rlewis(--nospam--at)techteam.org

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