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Re: ROOF DECK EQUIVALENT THICKNESS

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On Aug 14, 2005, at 6:13 PM, John J. Treff wrote:

Are there any formulae, tables or procedures to calculate the equivalent thickness of a roof deck as a flat plate? I'd like to use shells in a software program as roof sheeting and need to come up with an equivalent thickness for the shells since I can not input the steel sheet shape. I assume the material I will specify for the deck will be the same as the one the steel deck.
Nothing simple. I've tried doing this for corrugated courses making up grain storage silos, and it isn't simple. Your material needs to be orthotropic, since the bending stiffness is different normal to any stiffeners or joists is different than for the direction normal to the joists. Moreover the stiffness against direct inplane loading doesn't have the same relationship to bending stiffness as exists for an ordinary flat plate. You might have some luck if you can find out how the element stiffness is built up and from the orthotropic elastic moduli and material thickness and try to associate bending and axial stiffness for the deck in terms of the material variables in the element stiffness matrix. Then back calculate equivalent values for Elastic moduli and thickness for input to the FEA software.
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw/


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