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RE: Masonry Shear Pier Design - Balanced Strain Condition

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Bill,

Here's my stab at it off the top of my head .... (I'm not a masonry expert
by no means).... however, I would guess that it's similar to a concrete beam
that has a double layer in the bottom.  The "moment arm" between "T" and "C"
is measured to the centroid of the steel group (since the concrete below the
neutral axis does absolutely nothing for you.  Although in true reality, the
lower bars would start to yield first (due to their further distance from
the neutral axis)but as soon as they begin to deform the other bars pickup
and and resistance.  Now granted, in a wall, the bars would be space much
farther apart but if you're looking at a wall 40' long and the
"tension-compression" steel is in 3 or 4 cells of the masonry, the ratio of
"d" to the spacing of the tension steel (within one or two CMU blocks) is
fairly similar to the spacing of the tension steel relative to "d" in a
double layered concrete beam.  Just a stab it ....... Any comments ?

Robert

-----Original Message-----
From: Bill Allen [mailto:Bill(--nospam--at)AllenDesigns.com]
Sent: Friday, August 25, 2000 2:28 PM
To: seaint(--nospam--at)seaint.org
Subject: Masonry Shear Pier Design - Balanced Strain Condition



I understand a balanced strain condition for a shear pier with bars only on
the outermost cells, but how does one determine a balanced strain condition
for a shear pier with distributed steel (bars in every cell)? It would seem
like to me that, if the outermost bars only were at a strain of Fy/Es, then
the interior bars would be at fs<Fy and the Moment Mn would be less than
that for the condition where P=0.

Any help?

TIA,

Bill Allen, S.E. (CA #2607)
ALLEN DESIGNS
Consulting Structural Engineers
Laguna Niguel, CA
http://www.AllenDesigns.com
V (949) 365-5696
F (949) 249-2297


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