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MASN - Allowable Shear

• To: seaoc(--nospam--at)seaoc.org
• Subject: MASN - Allowable Shear
• From: rlewis(--nospam--at)techteam.org (Richard Lewis)
• Date: 04 Oct 1997 22:50:51 GMT

I am studying to take the NCEES structures test this Fall and came across
something I would like to get other opinions.  I have a copy of NCEES study
guide which gives sample questions.  A masonry question call for the design
of a lintel.  It is based on the UBC code.  I don't usually use this code for
masonry design.  I prefer the ACI code.  The problem is based on UNINSPECTED
values.  1994 UBC 2107.1.2 states

"when quality assurance provisions do not include requirements
for special inspection as prescribed in section 1701, the allowable
stresses for masonry in section 2107 shall be reduced by one half".

Now, I interpret this to mean I calculate the allowable stresses for bending,
compression, shear, etc. and then divide it by 2 to find the maximum
allowable stresses.  My question comes from the answer to the sample problem
for shear.  The code equation is:

Fv=1.0*SQR(f'm)         (7-17)

The solution for the sample question was as follows:

Fv=1.0*SQR(f'm/2)

My interpretation of the code is:

Fv=[1.0*SQR(f'm)]/2

Which is right?

Also, I thought for masonry design the critical section for shear was at a
distance of 'd' from the face of support, like concrete, but I can't find
this in the UBC.  Did I miss it, or am I wrong?

While I'm at it, allowable shear and tension values for bolts, should they be
halved for uninspected construction?  The code as stated above specifically
states "allowable stresses for masonry" are to be halved.  What about
hardware?
__________________________________________________

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

The service mission like-minded Christian organizations
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