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RE: Slender Masonry Walls

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Kipp,

I don't think that "slender wall" is pushing the envelope.  It has been
tested by the NCMA and has been around for a long time.  

But, even if you can make the basic wall work, you wind up fighting the
details.  When you calculate the concentrated out of plane forces from the
lintels at openings like doors, louvers, and windows, it becomes a struggle
to make the numbers work.  What happens is that the concentrated loads from
the lintels get dumped into a vertical element that has the "b" dimension
cut in half because of the opening.  The stresses then go out of sight.

In tall walls you often have to stick a structural tube in the wall to take
the out of plane lintel loads.

Regards,
Harold Sprague
The Neenan Company

-----Original Message-----
From: Kipp Martin [mailto:KAMartin(--nospam--at)carollo.com]
Sent: Monday, April 19, 1999 9:06 AM
To: seaint(--nospam--at)seaint.org
Subject: Slender Masonry Walls


I recently completed a design for a masonry building with walls 27'-0" tall
using 8 inch CMU.  I followed the Load Factor Design method of the 1997 UBC
and satisfied both the strength and serviceability requirements.  A senior
co-worker has questioned my design, primarily because the h/t ratio is over
40.  He says that the "slender wall" design approach is "new and untried"
and "pushing the envelope".

I have not heard of any problems associated with properly designed and
detailed slender masonry walls.  I don't consider the design method
particularly "new" as the publication that I reference was printed in 1986.
Am I "pushing the envelope" designing a 27 foot tall wall with 8 inch block?

--Kipp A. Martin
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