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RE: Steel lintel beam

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If you don't provide control joints, you'd better reinforce that wall.

50'-0" exceeds the limit from the masonry institute for control joint
spacing
(20-25')

When the masonry expands due to thermal variations, it will displace
horizontally without
Control joints.

If you treat the parapet as a deep beam, what stabilizes the compression
component?

Won't it laterally buckle?



I was just at a warehouse last week (similar construction) with this
condition...that's what happens to the masonry parapet when no provision
Is made for expansion/contraction (lack of control joints).


You are correct, masonry doesn't crack in compression, but it does crack in
(flexural) shear.

Regards,

David L. Fisher, SE, PE
Senior Principal
Fisher+Horos Structural Engineers
372 West Ontario
Chicago, IL 60610
USA

312.573.1701
312.720.0505 mobile

www.fplushse.com

-----Original Message-----
From: Fountain Conner [mailto:fconner(--nospam--at)pcola.gulf.net]
Sent: Tuesday, May 22, 2001 8:44 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Steel lintel beam

Let me throw a tidbit or two in here...

*If* the wall above the steel beam is continuous, w/o openings, why not
consider???

...using it as a simply supported beam with the masonry in compression and
the steel working in bending *and* as tension steel in a "deep" beam.

You can shore the steel beam until the masonry is placed and cured.  You
can fill and reinforce the block cells, etc., and make a composite section.
 Your deflection can be slightly lessened, but this will be somewhat offset
by creep.

Of course, you can accomplish the same thing with a less-vigorously
reinforced masonry wall and a fairly heavily reinforced "bond" beam at the
top for the "top flange" of this monster.

Another possible solution (probably the most practical) would be a "poured"
concrete lintel.  The depth/span ration should be okay.  This sounds like a
parapet wall.  Can you brace down from the top to the roof structure?
Otherwise you're trying to cantilever from a "pinned" connection.

Control joints in the beam span have been mentioned.  I think they are a
bad idea.  A joint at each end will take care of the rotation.  In the rest
of the span, the masonry will be in compression (If you shore during
construction).  And masonry in compression is not given to cracking.

My 2 cents...

Fountain E. Conner, P.E.
Gulf Breeze, Fl. 32561


----------
From: Javier Encinas <jencinas(--nospam--at)coqui.net>
To: seaint(--nospam--at)seaint.org
Subject: Re: Steel lintel beam
Date: Monday, May 21, 2001 5:27 PM

Ed:

A 50-ft long simply supported beam with such a high load (8' x 70 psf = 560
plf) and deflection limits (L/600) would be a monster. I rather would
suggest to form an 8-ft high vierendel truss, either in steel or concrete.
The open spaces could be filled with block and plastered. This way the
members would be much lighter and the deflections smaller.

Javier Encinas
ASDIP Structural Software
www.asdipsoft.com
  ----- Original Message -----
  From: edjonson
  To: seaint
  Sent: Monday, May 21, 2001 10:58 AM
  Subject: Steel lintel beam


  I have a question about using a wide flanged steel beam for supporting an
opening in a masonry wall.  The opening is 50 feet, with 8 feet of masonry
wall above.  I'm planning on using a steel beam, designed as simply
supported.  I have two questions.
  1. What deflection limits should I use for the steel beam?  Also, should
the dead load from the roof joists be considered as live load?

  2.  If I design the steel beam as simply supported, is there a potential
problem with cracking in the masonry wall due to negative bending stresses?
  I have a low roof that frames in to the side of the masonry wall at the
same level as the steel beam that will lateral support the steel beam.
  Thank you for any guidance.
  Ed Jonson


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