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Re: Plywood shearwall in Plumbing Wall

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Dave and Dennis,

Dave grasped what I was shooting for, my analogy is better demonstrated with
a sketch. Point was that a shear wall is just like a cantilevered beam fixed
at the foundation (shear along the length of the web/drag plate tension &
comp at the extreme fibers). Now if you rotate the whole model 90 deg it's
just like the classic cant beam from static's as shown in AISC 9th ed ASD
page2-303 #22. Now if the plywd and studs were replaced with a say W24 with
flanges attached to the supporting member to transfer tens&comp and the web
is
fillet welded to the support. Now say I only weld 10" of the web---5" down
from the bottom of the top flange and 5" up from the top of the bottom
flange (say 10" of web or so unwelded) because that's all that is needed to
resist the load.

Dennis do you think the W24 acts as two beams or does it act as one beam? To
me it works just fine just as a single beam--just as discontinuities in the
bottom plate are ok as long there is enough drag strut available. also
remember the bottom plate is just transferring the shear load from the plywd
to the anchorbolts. The bottom plate (and the A.B.) is just like the fillet
weld in my analogy. The steel beam doesn't fall apart just because the web
is not continuously tied to the support.

 I may need Dave to translate again...

Best Regards,

Rand




----- Original Message ----- 
From: "Gale45man" <gale45man(--nospam--at)yahoo.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, June 30, 2004 3:03 PM
Subject: Re: Plywood shearwall in Plumbing Wall


> I'm not certain I grasped Rand's parallel, either, but
> I believe he has a point regarding the original
> question about one plumbing hole in the bottom wood
> plate of a shear wall that is bolted or otherwise
> connected to a foundation wall or slab (that is, a
> hole in a mudsill plate...not top plates or headers or
> whatever).
>
> The situation posed in the original question is not
> much different than a mudsill with an unreinforced
> splice between two adjacent plates that are butted
> together to make a long run.   While we'd all like
> Contractors to use mudsill plates as long as possible,
> and we usually require bolts within X inches of the
> ends of mudsill plates, I bet it is the rare engineer
> who requires straps across joints between two adjacent
> plates.  If the mudsill is not designed to be a
> collector (dragging load from one horizontal location
> to be resisted at another more distant location), and
> if the mudsill bolts or other connections to the
> foundation are fairly closely spaced, I don't see a
> problem with either unreinforced butt joints or the
> occasional hole from a pipe.  If if if if if...
>
> d a v e   e v a n s
>
>
> Rand,
> I don't think the parallel exists in your argument.
> Shearwall capacity is
> based on tested results with all elements of the
> shearwall in tact. Once
> you remove a portion of the plate, you introduce a
> hinge - actually two
> since there is some length to the discontinuity. Now,
> it you want to
> design the wall on either side of the discontinuity as
> two shearwalls, you
> are free to do so, but please provide a rational
> analysis of how you
> transfer the shear (assuming the solid panel above the
> discontinuity acts
> like the drag element of a panel above the window or
> door header) across
> the discontinuity through the use of blocking and
> strapping. This is not
> done and IMO the wall loses capacity or becomes two
> walls with
> insufficient resistance to uplift and non-conformance
> to code required
> aspect ratio's of non-proprietary walls.
>
> Whew! If you destroy a structural element, and for the
> moment let's
> consider the shearwall to be one element composed of
> multiple components
> that work together to produce the resisting capacity
> needed to meet the
> calculated demand (lateral force), then you should be
> able to repair it
> and provide proof through a rational method of
> mechanics as to how the
> repair should be made.
>
> I guess I am becoming redundant (give me one for rho).
>
> Dennis ;0_)
>
>
> Dennis S. Wish, PE
>
>
> California Professional Engineer
>
> Structural Engineering Consultant
>
> dennis.wish(--nospam--at)verizon.net
>
> http://www.structuralist.net
>
>
>
>
> -----Original Message-----
> From: Rand Holtham, P.E.
> [mailto:rand(--nospam--at)sigmaengineers.com]
> Sent: Tuesday, June 29, 2004 1:59 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Plywood shearwall in Plumbing Wall
>
> Dennis,
>
> let me play Devil's advocate here, What failure are
> you concerned about?
> By analogy lets say we have a steel cant. stub beam on
> the side of a
> column. Connect the stub to the column with a welded
> moment connection.
> let's say I cut a section of the web out at the column
> to stub beam
> connection. will that completely violate the
> connection capacity? No. Is
> it as strong as it could be? No. Will it support the
> load? maybe, depends
> on the load. Therefore it is conceivable that you may
> be nit picking a
> bit.
>
> My humble opinion,
> Rand
>
>
>
> ----- Original Message ----- 
> From: "Paul Feather" <pfeather(--nospam--at)SE-Solutions.net>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Monday, June 28, 2004 8:53 PM
> Subject: Re: Plywood shearwall in Plumbing Wall
>
>
> Plumbing penetrations in a shear wall plate is a very
> real concern,
> depending on the size of the pipe there may be very
> little plate left.
> Another problem aspect is when the penetration is in
> the top plates on
> multi-level projects.  The assumed top plate drag line
> is virtually
> severed and requires proper detailing to perform as
> intended.
>
> We avoid using plumbing walls as shear walls.  I do
> not think you are
> being unnecessarily concerned.
>
> Paul Feather PE, SE
> pfeather(--nospam--at)SE-Solutions.net
> www.SE-Solutions.net
>   ----- Original Message ----- 
>   From: Dennis Wish
>   To: Light_framing(--nospam--at)structuralist.net ;
> seaint(--nospam--at)seaint.org
>   Sent: Monday, June 28, 2004 6:21 PM
>   Subject: Plywood shearwall in Plumbing Wall
>
>
>   I&#146;m not sure how big a problem this is, but I
> am running across it a lot
> in plan checking light-framing. The engineer or
> architect of record is not
> paying attention to the location of designated shear
> walls and is placing
> walls where plumbing will penetrate the mud sill. By
> design, I am careful
> to avoid this as I believe it destroys the continuity
> of the shearwall
> plate. I &#146;ve had situations where walls were
> accidentally placed in a
> plumbing wall and I have worked out details using 2x
> solid blocking placed
> between studs and secured with the 2x edge down
> against the remaining wood
> sill plate. I then end-nail the blocks through the
> studs and consider the
> plate to be repaired (once the plywood is nailed to
> the face of the block
> above the plate cut-out.
>
>
>
>   I am seeing this a lot and pointing it out as a
> correction, but since
>   the
> code does not specifically address this issue, I
> don&#146;t know if I am
> raising unnecessary concerns.
>
>
>
>   What are some of your opinions on shear walls in
> locations where the
>   plate
> is interrupted or made discontinuous due to a utility
> or drain?
>
>
>
>   Thanks in advance,
>
>   Dennis
>
>
>
>   Dennis S. Wish, PE
>   California Professional Engineer
>
>   Structural Engineering Consultant
>
>   dennis.wish(--nospam--at)verizon.net
>
>   http://www.structuralist.net
>
>
>
>
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