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Pre-Eng Building Companies

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List,

I often design foundations for pre-engineered metal buildings and I wondered
if any of you have had similar problems with the way loads and load
combinations are given. I find that they are too vague. These pre-eng
building companies give the following data: dead load, collateral load,
lateral seismic load, longitudinal seismic load and partial roof loads 1
thru 3 or 4. These are not too bad as you can usually figure out what they
are, with the exception of pattern loads. They usually don't say what the live load (as opposed to snow load) is -
you have to figure out that it is non-existent.

However, the real problem arises with wind loads and crane loads, e.g.,
lateral primary wind loads 1 thru 6 and longitudinal wind loads 1 thru 6.
They never say whether the wind is from left to right or vice-versa or
whether it contains internal suction or pressure. They leave it up to the
engineer to determine what they are and whether or not they are applicable
to the foundations. The same is true for crane loads, particularly if there
is more than one crane. Crane Load 1 thru x or Crane Load Left (or right) 1
thru x without saying whether these contain horizontal thrust or not.

I have dealt with as many as nine different PEMB companies and I think
Butler's are the best in that they actually give you individual loads, i.e.,
wind left, wind right, internal suction, internal pressure, etc., and allow
you to choose the proper load combinations. On the other hand, I truly
dislike Robertson Building Systems loadings as they give you all of these
different wind or crane combinations as described above without telling you
what they consist of. It would not require any changes to their program to
inform one what the combinations consist of, just put the definitions in the
preamble to the loadings.

Another beef is that the Robertson loads for preliminary design are never in
the same order as the final loads that are issued later.

I don't believe that there is any difference between PEMB companies in the 2
countries as most the computer programs have originated in the US and are used
in both the US and Canada.

What is ironic about these loadings is that some of these PEMB manufacturers
put a note with their loadings that the foundations are the sole
responsibility of the foundation designer.

Cheers,
Gary


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