] [Thread] [Date] [Author]

[billp(--nospam--at)neosoft.com (Bill Polhemus)]

On Thu, 7 Sep 1995 19:47:23 -0700, lhoward(--nospam--at)silcom.com (Lynn Howard) wrote:
> >How would YOU set the THICKNESS parameter in order to model the shear  
> >stiffness as precisely as possible?  Not sure, but I believe there is  
> >an equation for this set for in (I Believe) the SDI Manual (a copy of  
> >which I do NOT possess!)
> >
> >Any assistance would be MOST appreciated.
> >
> 
> You did not mention what type of floor or roof you are trying to model.
> Since you mentioned the SDI Manual, I assume you are trying to model a metal
> deck.  If you are modeling a floor, and you have several inches of hardrock
> concrete over the metal deck, I would model the floor as a concrete element,
> using the average thickness of the concrete.

You are correct; I do mean a metal deck.  And what if you're using, say 
3.5" to 4" of lightweight concrete for your floor deck?  Would you still
disregard the contribution of the deck?

> If you are modeling a roof which does not have a hardrock concrete fill over
> it, then it can become more complicated.  It is important to know if you are
> going fasten the side laps and end connections (by welding, button punching,
> or screws).  This can effect the overall stifness.  
> I have an older SDI manual, but on pages 21 to 31 it discusses
> the question
> of diaphragm stiffness, and proivdes example problems.

I guess I just need to get a copy of the manual!

> If you have a very stiff metal deck (thick guage, that is supported at close
> intervals by joists, screwed or welded side laps and a lot of puddle welds
> at the ends), you have have to calculate the overall stiffness, and then
> approximate an equivalent flat plate.  You can then adjust the E and G in
> the vertical direction to compensate for the fact that it is modeled as a
> thin plate element.

Seems to me this is the situation I would have.  Thank you.

> 
> Hopes this helps [and I hope everyone won't tell me I'm wrong about this :)]

Well, so far no argument from ME!

*-------------------------------------------*
*      William L. Polhemus, Jr., P.E.       *
*                                           *
* "I'm not an intellectual...but I play one *
*  on the Internet..."                      *
*-------------------------------------------*
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