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RE: ROOF DECK EQUIVALENT THICKNESS

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> JJ,
>
> This is the approach that I took once to include a flexible metal deck
> in a FEM model.  I took the example on pg. 68 of Vulcraft's roof deck
> manual and created a model with shell elements that had the same loads
> and dimensions as the example.  The thicknesses of the steel shell
> elements were then varied until the deflection in the model equaled the
> deflection in the example.  This gives the equivalent thickness for the
> roof deck with a particular fastening pattern.

You stole my thunder. :-)

This is exactly what I have done.

N.B. you will find that the equivalent thickness is VERY thin, on the
order of something like 0.01", perhaps less. Make sure that you don't have
loads directly on the "diaphragm" in your model which the diaphragm
element is expected to resist in flexure, because it will blow up.

In fact, make sure there are NO LOADS AT ALL, even self-weight, that can
deflect the diaphragm out-of-plane--because it will blow up.

Bill "bown up a lotta models in my time" Polhemus, P.E. (Texas & Alabama)


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