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RE: Concrete bearing Edge Distance

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".... if the steel beam will see any thermal changes ..."

The beam WILL see thermal changes, if not only due construction (day to
night, rainy day to sun beating down day, not mention any seasonal
changes).  You should always allow for thermal expansion contraction of
steel when attaching to concrete or CMU.  If it must be a connection
that does not allow movement at the concrete/steel connection, the steel
beam must be able to make up the movement at the other end of the beam.
Thermal forces can be VERY high.


Charles F. Espenlaub, III, P.E.
Martin-Espenlaub Engineering



-----Original Message-----
From: Jake Watson [mailto:jwatson(--nospam--at)inconnect.com]
Sent: Friday, March 24, 2000 9:36 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Concrete bearing Edge Distance


Chanel1096(--nospam--at)aol.com wrote:
> 
> The info in PCI is very close to the info in ACI318 section 10.17 so I
will
> give some more detail as to my question.
> The question comes from a residential building where there is a steel
beam
> bearing on a concrete wall.  The problem is that the beam only bears
~1.5" on
> the wall. We are fixing the bearing problem but that is where my
question
> comes in.  How do you determine how much bearing length you need for
the beam
> on concrete based on the edge distance?
> 
> -Bill King, EIT
> 
	Your an E.I.T. like myself so I will assume your using LRFD.  In
volume
2 of your manual there is a sample problem discussing exactly what your
talking about.  I don't have the page number in front of me though.  If
you look at the bottom of the uniform beam loading table (not charts) in
volume 1, you will see lots of Rn style numbers.  The first one is shear
(phi*Vn) then I believe the next 2 are some sort of Rn (see sections
K1.3 and K1.4).  Those go into empirical formulas for determining things
like web crippling, yielding at the face of support, etc. Track down
where those numbers are used.
	Some other things to check: crushing of concrete (enough
baseplate
area?), baseplate design.  Also, as a side note: if the beam will see
any thermal change, use slotted holes to attach it to the wall.  If the
beam expands or contracts because of temperature and is fixed to the
wall, it will move or simply break the wall.
	If you need more help, email me privately and I will send you a
MathCad
sheet in HTML that will work a sample problem for you.

Best of luck,
Jake Watson, E.I.T.
Salt Lake City, UT