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RE: Commercial Bldg. - Second Floor Loads

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TIm,

I can actually understand Denise's confusion.

There have been several responses that would have pointed out the same
information that I would have, but none have picked up on the "real" point
of confusion that Denise seems to have (and neither did I until she
provided the direct point to it).

The point of confusion as it seems to me is that the UBC specificly
dictates that partition loads be considerd as dead loads, as Denise
pointed out in reference to section 1606.  This is completely different
than the IBC, BOCA, and ASCE 7 which put partition loads into the live
load category (and that is what I am used to).  The end result is that the
UBC requirement places her directly at odds with the advice that others
have given her, including YOU.  Your "standard way" of doing things (80
psf reducable plus 20 psf unreducable for partitions) would technically be
out of compliance with the UBC code (and BTW, this is how I am used to
doing it too, but then I don't live in UBC country <grin>).  While this
"technical violation" is not really a problem (it does not really matter
if it is DL or LL if you are doing ASD design and is just too consevative
compared to the UBC requirement if treated as LL and if you are using
LRFD/factored design), it still could be viewed as an "ethics" problem by
someone.  Thus, your standard way, while commonly accepted and used, would
seem to be at odds your statement about following the rules of ethics
(admittedly by a very loose interpretation).

The end result is that I have to agree that the ethics comment seems a
little out of line to me.  After all, if we are going to call into
question the ethics of anyone that doesn't fully understand something
(even something that may appear abundantly easy to understand), then just
about everyone on the list would be "violating" ethics rules.

Now, as to the original question...

As others have pointed out, office space is listed as 50 psf in codes such
as IBC, BOCA, and ASCE 7.  Corridors on floors other than the first floor
are listed as 80 psf for LL.  And partitions are supposed to be included
in the LL (except in UBC land).  As pointed out by others, a partition
allowance is to be inlcuded in office and other buildings where partitions
are subject to change UNLESS the LL exceeds 80 psf.  The partition
allowance in this case is NOT to be less that 20 psf.

The end result is that under these circumstances (i.e. IBC, BOCA, or ASCE
7) the "office" space could be designed for 50 psf LL (reducable) plus 20
psf for partitions (unreducable).  Most structural engineers (including
myself) will realize that the location of the corridors relative to the
offices will likely change in the future so they will actually use 80 psf
LL (reducable) plus 20 psf for partitions (unreducable), but could also
just use 100 psf LL (reducable) and NO partition allowance
(potentially depending on how one defines "specified live load"
[i.e. is it the live load chosen by the engineer to actually use
or is it the minimum code LL "spelled out" in the code] permitted by code,
but not what I would recommend myself).

Now, if you are following in the UBC, then it would seem that the "smart"
thing to do would be to use the 80 psf LL for corridor loading through
out (reducable), then allow for 20 psf in partitions under the DL as
dictated by the code.

Now, to me the real question (or at least one of them) should have been
does it seem logical to use office loading for this type of "application".
It sounds as if the space will likely be used as office space, but could
have more "TV" related uses.  The original post did not spefically state
that it would be actually office space, but that seemed to be the
implication.  At least one person thought that it might be used for other
purposes.  Thus, if it is to be used as actually office space then the
above information would still be valid.  If the space could be used as a
studio or some such, then it might be necessary to re-look at the whole LL
issue.

I also have to wonder at least a little at the 14 psf for dead load.  At
face value (without doing some calcs on my own), that seems a little light
if you end up with gyp ceiling below, plus carpet, mechanical, electrical,
and potentially some insulation for sound, not to mention the plywood and
wood framing members.  But, then again I don't do too much wood framing.
<grin>

HTH,

Scott
Ypsilanti, MI


On Wed, 25 Sep 2002, Timothy P. Spengler wrote:

> This isn't rocket science buddy.  Determining the floor load for mezzanines is pretty basic stuff.  Sure, engineers will have different schools of thought on how to precisely interpret the floor loading requirements.  But when it comes right down to it we all follow an almost identical, logical approach on how a floor will be loaded up.  If this was my project I'd be spec'ing the joists for 80+20, and designing the beams for a reduced 80 and an unreduced 20. That's usually what an architect means when they say the want 100 psf LL.  In fact I would bet that 95% of the office space in the U.S. isn't designed for anymore load than this.
>
> The purpose of my "crack" is to hopefully wake you up.  Like I previously implied, your thought process is irrational.  There are many other aspects of designing mezzanines that are quite a bit more complicated than this.  If your having trouble with this concept, I'm not convinced your going to fair very well with the rest of your design.
>
>
> -Tim
>
>
>
>
>
> -----Original Message-----
> From: DRPFLY(--nospam--at)aol.com [mailto:DRPFLY(--nospam--at)aol.com]
> Sent: Wednesday, September 25, 2002 4:57 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Commercial Bldg. - Second Floor Loads
>
>
> Tim--
>
> Do you think I should  design the trusses for full live, dead, AND partition
> loads?
> I don't understand the crack about " ethics".  I just want to design the
> floor framing correctly.  That's why I'm asking for advice from engineers who
> know more than I do about the subject.  Seems like there is more than one
> school of thought out there on including partitions as a separate load that
> may or may not be permanent and swapping LL values for partitions the UBC
> regards as DL.  I don't think I'm the only one who is confused.   Too bad I'm
> not as brilliant as you are.  You seem to know all the answers.
> Have a nice day.
>
> Denise Poeltler, P.E.
> The Flying Buttress
> Palm Desert, CA
>
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