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Re: Databases for lt gage steel

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I don't know about light gage, but for bar joists you are absolutely correct.
K-series and LH-series joists, as well as joist-girders, are custom designed for
each job.  And if the job is big enough some joist fabricators will commission a
special rolling a few thousands thicker or thinner to use the steel as
efficiently as possible.  Don't bother wasting your money on FloorVib2 if all
you want is the joist properties, as those used in the program are approximate
only.  They can't be exact because each joist is custom designed for each job,
as I said before.

If you purchase a particular joist today, and the same joist tomorrow, from the
same manufacturer, there is no guarantee they will be the same.  And from
different manufacturers, or from the same company but made in different plants,
there is practically a guarantee that they will be different.  They will all
meet whatever properties you specified, but anything you didn't specify may be
different.  So if you need chord width for stud attachment - specify it.  If you
need minimum (or maximum) moment of inertia - specify it.  If you need a certain
web opening or panel spacing for your mechanicals - specify it.  If you need
minimum angle thickness for longevity in a corrosive environment - specify it.
And of course if you need a certain strength or stiffness - specify it.

I was on a job recently that had over 5,000 joists and 600 joist-girders.  All
from the same manufacturer.  They all had 4' panels EXCEPT FOR 3 BAYS!  The
mechanical contractor hadn't yet seen this yet.  His first reaction when I
pointed it out was to cut out any webs that interfered with his duct runs.  If
the EOR had specified that all joist panels must line up, there would not have
been a problem.  But all he specified was strength, so that's all he got.


William Keil wrote:

> Does anybody know why the properties of joists are not published?  My theory
> is that each joist is rolled specifically for each loading detailed on the
> drawings and if they can roll the angles 1/32" thinner or shorten the angle
> legs by a 1/4" and still meet your loading/span criteria, the manufacturer
> will do it to save material and increase profits.
> I recall seeing K-joist properties being included in the FloorVib2 program
> offered by STRUCTURAL ENGINEERS INC., 537 Wisteria Drive, Radford, VA
> 24141, 540.731.3330, 540.639.0713 FAX.  Cost is $250 plus $10 s/h plus VA
> sales tax if you are a resident.  If I do more work with composite joists I
> would invest in this but right now the price is too steep just to get joist
> properties.  Because once you have the joist properties, you will need the
> joist girder properties and you are back where you started ... looking for
> unpublished data.  Good luck!