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RE: Clay/brick smokestacks

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I presume that this is an unreinforced brick masonry stack. 

If you are applying forces and using the ACI 530 for evaluation, you will
probably not be able to make the numbers work.  I imagine that the brick
masonry in flexure is being governed by tension across the bed joint.  The
brick should not limit you in tension, but the mortar will.  If the
construction is composite with a grouted space the tension could be governed
by the grout.

Occasionally the outer wythes of brick masonry chimneys were constructed
with spaced soldier bricks or embedded steel which put sections of the
mortared joint in shear as the stack is in flexure.   The spaced soldier
bricks produce a substantially stronger joint than a normally coursed brick
masonry bed joint.

This can be calculated, but it is best to pull prisms and test them.

Testing will also give you the strength of the mortar, and the brick
strength to determine the f'm.

I had good results using the Erlin Hime Labs of Wiss, Janney & Elstner.  You
have to be very careful in sampling and shipping to the labs.  You might
also consider getting a petrographics test done to get a design on matching
mortar for any repairs and tuck pointing (if required).

Even if you had the names of the brick supplier, the material properties
will still be a guess unless you test.

Harold Sprague

-----Original Message-----
From: Walkleypa(--nospam--at) [mailto:Walkleypa(--nospam--at)]
Sent: Wednesday, February 17, 1999 12:11 PM
To: seaint(--nospam--at)
Subject: Re: Clay/brick smokestacks

We are conducting a study of an 115' smokestack constructed in the sixties,
am looking for a possible source name or other information for what is
brick or clay blocks that have an exposed face of 5" by 7" by various depths
to form a 16" wall and a 12" wall. The "bricks" have holes making them
or semi-solid.
The base diameter is 10.5' and by calculation seems over stressed due to
tension, so I am hoping the original material has better properties than
assumed(guessed at) so far.