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RE: PEMB / Masonry expansion joints

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Has any research been done on thin brick veneer over
stud backup?  A previous employer manufactures light
gage wall panels with a 5/8" (or so) thin brick
mortared onto metal lath over a densglass and stud
frame.  The system got real expensive

Where the l/600 is set to limit the crack opening at
the face of the brick, it would make sense that the
thinner the brittle finish, the more the system could
bend before the same crack opening would occur.  We
always used l/600 for the system, regardless - even
when the occasional spec only called for l/360.  We
complained when the specs called for l/720.

Problems developed when the architects detailed 18ft +
floor-to-floor heights without wind girts, yet
specified l/600 or l/720 for stud framing.

Jim Wilson

--- Harold Sprague <spraguehope(--nospam--at)hotmail.com> wrote:

> Bill,
> When the AISC developed Design Guide #3 it was
> predicated solely on the 
> serviceability of single story structures.  That is
> where the serviceability 
> concept of the the 10 year wind was introduced. 
> Keep in mind that a 10 year 
> wind velocity will have about 75% of the pressure
> generated from a 50 year 
> wind velocity.  It would not be overly conservative
> to design the frame for 
> a h/200 lateral drift for the full 50 year wind.
> 
> The L/600 was a limit that came from studies from
> the Brick Institute of 
> America, and is what the BIA recommends.  Hardly any
> solid brick walls are 
> used today so a conflict of interest is unlikely
> with the BIA.   The L/720 
> is also the recommendation of "Technics - Steel Stud
> / Brick Veneer Walls", 
> by Trestain and Rouseau for The Canadian Mortgage
> and Housing Corporation 
> (CMHC).
> 
> The only published documents that have pushed the
> L/360 for brick is the one 
> generated by The Metal Lath / Steel Framing
> Association.  Obviously they 
> have a vested interest in pushing for wider use of
> metal studs as opposed to 
> brick with a CMU back-up.
> 
> Some years ago, I had panels tested for water
> infiltration and wind, and it 
> led me to the same conclusion of the BIA.  The
> underwriters on that 
> particular building would not underwrite the
> building for any greater panel 
> deflection.
> 
> Regards,
> Harold Sprague
> 
> 
> 
> 
> >From: "Sherman, William" <ShermanWC(--nospam--at)cdm.com>
> >Reply-To: <seaint(--nospam--at)seaint.org>
> >To: <seaint(--nospam--at)seaint.org>
> >Subject: RE: PEMB / Masonry expansion joints
> >Date: Fri, 20 May 2005 09:39:45 -0400
> >
> >I agree with much of what Harold wrote below, but I
> personally question
> >the use of 10-year wind speeds for serviceability
> checks. That seems
> >find if you are only concerned about "comfort" of
> occupants due to sway,
> >but if you are concerned about cracking of masonry,
> I feel that 50-year
> >wind speeds should be used if the building has a 50
> year design life.
> >Thus, I prefer an H/200 limit on drift using full
> code wind pressures.
> >
> >While limits of L/600 to L/720 make sense for
> vertical deflection of
> >masonry supports, I'm not sure that should apply to
> lateral supports. A
> >masonry wall is very stiff in-plane but has some
> flexibility
> >out-of-plane. I feel that limits of L/240 to L/360
> would be reasonable
> >for lateral supports.
> >
> >William C. Sherman, PE
> >(Bill Sherman)
> >CDM, Denver, CO
> >Phone: 303-298-1311
> >Fax: 303-293-8236
> >email: shermanwc(--nospam--at)cdm.com
> >
> >
> > > -----Original Message-----
> > > From: Harold Sprague
> [mailto:spraguehope(--nospam--at)hotmail.com]
> > > Sent: Thursday, May 19, 2005 10:57 AM
> > > To: seaint(--nospam--at)seaint.org
> > > Subject: RE: PEMB / Masonry expansion joints
> > >
> > > Jim,
> > > There are several considerations that I would
> suggest for
> > > consideration.  It is important to note that
> this is a
> > > servicability issue, and not a life safety
> issue.  Therfor
> > > the building code is not much help.
> > >
> > > Lateral Drift:
> > > The standard for Butler Manufacturing for a
> masonry clad
> > > building is h/100.
> > > I would suggest that you obtain the AISC Design
> Guide #3
> > > "Serviceability Design Considerations for
> Low-Rise
> > > Buildings".  Reference p 17.  I prefer to limit
> the drift of
> > > the frame to h/200.  With proper detailing one
> can design to
> > > h/100.  It really does not cost that much to
> require an
> > > increase in frame stiffness when you look at the
> cost per
> > > square foot of the building.  Keep in mind that
> this drift
> > > limit is for a 10 year wind not a 50 year wind.
> > >
> > > Horizontal deflection:
> > > There is a lot of controversy on this issue, and
> the
> > > opiinions vary depending on who's is citing the
> research.
> > > The light guage people claim that you can go to
> L/360.  But
> > > the same research (the Clemson Study) cited by
> others would
> > > indicate L/720.  I have a bit of heart burn with
> the research
> > > itself because of the types of mortar either
> used or not
> > > properly cited.  N mortar is much better for
> crack healing
> > > than S mortar.  But that is another issue.  The
> Canadian
> > > Mortgage and Housing Corporation (CMHC) did an
> independent
> > > evaluation and suggests L/720.  But again, this
> is a
> > > serviceability issue, and this would suggest a
> 10 year wind.
> > > My preference is to use L/600 with a 50 year
> wind.  This is
> > > about the same as a L/720 with a 10 year wind. 
> The L/600 is
> > > consistant with the Brick Institute of America
> > > (BIA) recommendation.
> > >
> > > Vertical deflection:
> > > Obviously this one is L/600 as mandated by most
> building
> > > codes. You can go more with proper detailing,
> but why fight it?
> > >
> > > There have been several good articles in The
> Magazine of
> > > Masonry Construction on this issue.
> > >
> > > PS Use G-90 galvanized studs.
> > >
> > > Regards,
> > > Harold Sprague
> > >
> > >
> > >
> > >
> > > >From: Jim Wilson <wilsonengineers(--nospam--at)yahoo.com>
> > > >Reply-To: <seaint(--nospam--at)seaint.org>
> > > >To: seaint(--nospam--at)seaint.org
> > > >Subject: PEMB / Masonry expansion joints
> > > >Date: Thu, 19 May 2005 06:42:13 -0700 (PDT)
> > > >
> > > >If a metal building is designed to H/100
> lateral displacement, is it
> > > >appropriate to size the vertical expansion
> joints in the
> > > masonry facade
> > > >at the building's corners for an equal amount
> of movement?
> > > >
> > > >For example, 20ft tall building, masonry walls
> to 12ft tall.
> > >  Lateral
> > > >displacement = 2.4" at roof level, 1.44" at top
> of masonry.
> > > Expansion
> > > >joints in masonry should provide for
> 1.5"(1.44") lateral movement.
> > > >
> > > >This seems obvious, but is there anything else
> to it that I
> > > am missing?
> > > >
> > > >TIA,
> > > >Jim Wilson
> > > >Stroudsburg, PA
> 
>
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