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Re: Collateral ceiling load

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The actual load can vary depending on your actual systems, but 3 psf is
common for a preliminary value for sprinklers and some minor electrical.
The things to watch for on metal buildings are:

1.  The builder understand that these "collateral loads" are intended to be
predominantly hung through the Z-purlin webs and not "C-clamped" off the
outstanding leg of the purlin.   The actual attachment to the purlin is far
more critical than the 3 psf versus 5 psf debate etc.  Very light loads can
be C-clamped, but not medium to heavy point loads.

2.  I have found it easier to design the Z-purlins for a heavier load and the
frames for a lighter load as mentioned in one of the other postings.   For
example, if I put 10 psf on the purlins, the frames I may design for 5 psf.
Most of these loads are not truly "distributed loads" but typically become
isolated points load with some pattern to them.  In general,  a few purlins
get heavily loaded while most purlins have no additional load at all.
Purlins over aisleways or easily accessible areas during construction tend to
"attract loads" to these specific purlins.  I think the equation is "Purlin
accessible by ladder = overloaded purlin".   I think the 2nd derivative of
this equation is "construction problem"...or is that "finger-pointing by
contractor"?...I can never remember..

Hope this helps...

Ron Martin
Martin Stuctural Services, Inc.
Tuscaloosa, AL

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