Non-matching roof deck thicknesses

[Galambos]

Does anyone know if it is acceptable practice to have two different metal roof deck thicknesses (1.5 inch and 3 inch) on a roof diaphragm in a single story, seismic design category D, SCBF building?

I have a portion of the building that would be advantageous to use 3 inch accoustical deck with a ceiling finish, and other areas where the structure will not be exposed.

Thoughts?

 

[a2mfk]

From a diaphragm standpoint, I think if you model it as a flexible diaphragm it would be OK. But I would want to research it a little more. Have you checked out the Steel Deck Institute (SDI) manual or their website?

I am not fluent in seismic design but stiffness compatibility may be an issue depending on the rest of your structure.

You and the architect need to carefully coordinate details, if you have a parapet with scuppers for example..

HTH,
Andrew Kester, PE
Florida