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RE: CMU Lintels

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Richard,

I generally locate a control joint within about 2' from one side or the
other to keep a shrinkage crack from trying to form in the opening area.
This makes the column relatively small when compared to the lintel beam.
Therefor I size the flexural rebar in the lintel beam for a simple span
element.

Even if the compression block stays within the grouted section you still
should check the horizontal shear through the face shell and bedded joints.
Basically you have a composite section the same as concrete and structural
steel (the studs transfer the horizontal shear) or double walled fiberglass
(the polyisocyonate insulation transfers the horizontal shear).  I generally
grout the entire section that I use as a lintel.

There are some good examples of lintel design in the Corps of Engrs
Structural Design for Masonry  TM 5-809-3.

Harold Sprague, P.E.
The Neenan Company
harold.sprague(--nospam--at)neenan.com


-----Original Message-----
From: rlewis(--nospam--at)techteam.org [mailto:rlewis(--nospam--at)techteam.org]
Sent: Thursday, October 22, 1998 2:36 PM
To: seaint(--nospam--at)seaint.org
Subject: CMU Lintels


I want to get so others opinions on design of reinforced CMU lintels above
openings, specifically larger openings.  In the past I have designed
openings, say 9 feet wide for a garage door, by using the total depth of the
wall above the opening.  Since I almost always have a bond beam at the top
of
the wall I design the lintel as fixed ends using the bond beam reinforcing
as
top bars and the lintel reinforcing as bottom bars.  I check the shear based
on the entire depth of the wall above the opening and make sure it is
sufficient for unreinforced shear on the face shell width only.  I check the
depth of the compression block to be sure it stays within the solidly
grouted
top of wall bond beam and the lintel bond beam.

Does anyone see any problems with this design concept which I haven't taken
into consideration?



__________________________________________________

Richard Lewis, P.E.
Missionary TECH Team
rlewis(--nospam--at)techteam.org

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