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# masonry block properties

• To: <seaint(--nospam--at)seaint.org>
• Subject: masonry block properties
• From: "Andrew Kester" <andrew(--nospam--at)baeonline.com>
• Date: Wed, 30 Jul 2003 12:41:22 -0400

```To prove a point, I have to determine the allowable load for an unreinforced
8"x 16" section of block wall. Now I know I have to check everything
according to ACI 530-99, C-20, Sect. 2.2 Unreinforced Masonry. But, to
calculate the bending stress in the block, ungrouted with no reinforcement,
is completely different then standard reinforced masonry design. I am
assuming I would use the following regular engineering mechanics formula for
bending stress:

Fb= M/S

S- this is the problem, as it is hollow block. I cannot find any tables for
this, and I have quite a few resources. Does anyone have this value in a
table? Would it be improper to just hand calc the Sx for a 8"x16" hollow
block? Now would a simplifed way of doing this, to be calculate Sx for a
solid 8x16 block, then subtract the Sx for the cavities? This ignores the
curved cavity walls, and the thickness of walls is different on the top then
the bottom, etc.

I do not see why this is wrong, then I calc. Fb as I did above. The same
goes for Ix calc, which I need for formula (2-15) to calc Pe.

Thanks in advance. If you can directly CC me that would be great because I
get the digest list once a day.

Andrew Kester, EI
Longwood, FL

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