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Re: Load bearing exterior wall supporting the cladding

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Reza,

I would say that drift could be a concern for this type of cladding,
depending on the size and jointing the panels, the ability of the
connections to allow the panels to move relative to the metal studs, and
how tolerant of cracks in the panels that you are.

If the panels are relatively small and the joints between panels allow
some relative movement between panels, then drift may not be too much of
an issue.  The aspect ratio and orientation of the panels can also effect
this (i.e. are the panels square; are the panels long rectangle oriented
horizontally or vertically).  All of this variations can affect the
ability to accomidate drift.  Basically, if the panels are able to
accomidate movement with out putting too much load into adjacent panels,
then drift may not be too much of a problem.  In other words, if each
panel can move indepentently rather forcing other panels to move at the
same time by bearing against other panels, then drift can be less of an
issue.

If the panels are sized or oriented or jointed such that they are all
acting "together", then using some sort of connection that is rather
flexible so that the panels can move relative to the metal studs.  The
panels that are composite with the studs don't sound like this would be an
option.  Typically a "composite" connection is not too flexible.  If the
connection is flexible, then less load will be imposed on the panels
meaning that they are likely more tolerant of the lateral drift.

Finally, it is also a function of how tolerant of cracks in the panels you
(or your client) are.  Obviously, major cracks in the panels would not be
a good thing since that could allow moisture to penetrate the building
envelope.  Minor cracks, however, are more of an appearance issue.  If
some minor cracking is OK, then drift may be less of an issue.

The other thing to consider is that the type of cladding can actually
affect the lateral drift depending on how the cladding is attached to the
studs.  If the panels are attached to the studs such that they can move
relative to the studs, then the lateral drift will likely be higher
(largely dependent on the lateral system).  If the panels are attached in
such a way that lateral load can be "imposed" on the panels, then the
panels could actually begin to act as a part of the lateral system
(unintentially) which could actually reduce the amount of lateral drift of
the building, while putting significant load into the panels.  The end
result is that you probably want to make sure that the panels are attached
in such a manner that they don't unintentially become part of the lateral
system.  In such as case, then the panels must be detailed in such a
manner to be able to accomidate the movement of the building without
imposing too much load into the panels.

HTH,

Scott
Ypsilanti, MI


On Tue, 13 Aug 2002, Reza Dashti Asl wrote:

> Scott,
> Type of cladding:
> 1- Concrete thin shell panels(composite with the wall's steel studs)
> 2- Glass Fiber Reinforced Concrete panels with Flex Anchors(rod or bar 
> connecting the GFRC skin to steel studs)
> 
> Design loads are both wind and seismic(zone 3)
> 
> Thanks,
> Reza Dashti
> 
> 
> >From: Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu>
> >Reply-To: <seaint(--nospam--at)seaint.org>
> >To: seaint(--nospam--at)seaint.org
> >Subject: Re: Load bearing exterior wall supporting the cladding
> >Date: Tue, 13 Aug 2002 17:07:16 -0400 (EDT)
> >
> >Reza,
> >
> >This will largely be effected by the type of cladding being used, but also
> >the type of load to which you may be concerned with (i.e. wind or
> >seismic).  Some types of cladding are relatively immune to larger lateral
> >drift (i.e. low end metal siding) while others are very sensitive to
> >larger lateral drift (i.e. brick).  In additional to the cladding
> >material, the details of the cladding and cladding attachment will affect
> >the abilit of the cladding to accomidate lateral drift.
> >
> >Thus, a little more information will be needed before anyone can really
> >offer any advice.  And even then, the value of the advice may be somewhat
> >limited depending on how you choose to detail the attachment of the
> >cladding.
> >
> >HTH,
> >
> >Scott
> >Ypsilanti, MI
> >
> >
> >On Tue, 13 Aug 2002, Reza Dashti Asl wrote:
> >
> > >
> > > Hi,
> > > In a building with load bearing exterior steel stud walls, these studs 
> >are
> > > also supporting the cladding. Is drift a concern for the cladding in 
> >this
> > > system?
> > >
> > > Reza Dashti, P.Eng.
> > > Vancouver
> > >
> > >
> > >
> > >
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