From: "Sprague, Harold O." <SpragueHO(--nospam--at)bv.com>
Date: Tue, 25 Jan 2000 08:28:02 -0600
It sounds like the typical strip window scenario. I size the beam based on
the deflection the beam experiences when the brick is placed. I calculate
the deflections due to the DL of the curtain wall, partitions, and LL.
If you have closely spaced properly designed brick joints and window head
details, you may be able to accommodate more movement. This is where a
thorough analysis and engineering judgement is required. In brick veneer,
continuous strip windows can accommodate more movement than punched windows.
I tend to detail brick veneer to the extreme. I check all the details
including the architectural details and elevations.
I have had to go back and repair other engineer's work that did not properly
account for spandrel beam stiffness. It's expensive and no one is happy.
The nice thing about the BIA is you can say, "Look at their requirements. I
have no choice." But my favorite is, "If you want me to do something
contrary to a national standard, I will need a letter to that effect." I
have no letters in my "Contrary to national standard" letter file.
> -----Original Message-----
> From: David Handy [SMTP:dhandy(--nospam--at)trg.ca]
> Sent: Tuesday, January 25, 2000 7:52 AM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: brick veneer support deflection
> I agree with the methodology for openings within the brick. And I don't
> disagree with what you or Harold has said. In my case I am not dealing
> a small opening but rather the complete length of brick wall to be
> supported at each floor which is a lot of dead load. If I add the dead
> of the floor that is being supported then the beam size would take another
> large jump. I usually don't include the DL of the floor structure as it is
> already there before any brick is placed. I feel this is reasonable. In
> case of the BIA document it makes sense to add in the DL because it is
> based upon a load bearing wall which is complete then loading with the
> load of the floor. In my case the steel beam is supporting concrete floor
> system which has the lintel attached to the edge of the floor slab.
> Therefore the DL of the floor is already there caused the deflection.
> I have always used the full DL of the brick/block supported by the floor
> and the live load with L/720. Everybody thinks I am too conservative at
> this. The OWSJ manufacturers will always want to use only the live load
> nothing else.
> At 10:38 PM 1/24/00 -0500, you wrote:
> >Remember that the lintel is only going to support a small triangular load
> >providing the lintel is shored while the brick is being installed. I use
> >45 deg. triangle, but know that with brick it will probably be much less.
> >Once the brick gets about a foot or so higher than half the span
> >will arch (providing you have an adequate thrust block), regardless of
> >whether the lintel is shored or not.
> >BIA is Brick Institute of America. I do the same thing that Harold
> >does in designing lintels in following the BIA recommendations. The
> >and 0.3" limits are to prevent the triangular cracking that would occur.
> >Hope this helps.
> >A. Roger Turk, P.E.(Structural)
> >Tucson, Arizona
> >David Handy wrote:
> >>>Also: This is very strict, especially the 0.3" in one case this would
> >L/1100. Would it make sense to use shear studs on the perimeter beams to
> >increase stiffness??? I would likely use a lesser amount for lateral
> >support reasons anyway. I don't use shear studs too often; would the
> >increase in stiffness be considerable or marginal?
> >thanks again, David Handy
> >At 06:36 PM 1/24/00 -0600, you wrote:
> >>The UBC says to use L/600 for total deflection. The BIA says the lessor
> >>L/600 or 0.3". I tend to agree with the BIA unless you can cut the
> >>into smaller panels with properly detailed joints that can accommodate
> >>movement. I would recommend that you read the BIA Technical Note 28B.<<
> >******* ******