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Gypsum Roof Deck Diaphragm Shear

Gypsum Roof Deck Diaphragm Shear

Gypsum Roof Deck Diaphragm Shear

(OP)
Does anyone have any resources or experience using a bulb T and gypsum roof deck as a roof diaphragm.  This is an existing building with bar joists and steel roof girders.  However there is no horizontal "x" bracing at the roof level.  I need to do a lateral analysis of the building due to increases in parapet height. Any comments would be appreciated.  

RE: Gypsum Roof Deck Diaphragm Shear

If I remember correctly - the IBC allows about 75 plf for gypsum on walls.  I presume you could use that on a roof.

Not much and not very good.  See IBC 2003 or 2006

RE: Gypsum Roof Deck Diaphragm Shear

(OP)
Thanks Mike.  I have seen that section, however I have reservations to use that value since this Gypsum deck sits on bulb tees and I would have a difficult time comparing the typical 12" o.c. fastening of gypsum walls to studs with the bulb tees every 3'-0" o.c. or so.  I do appreciate your input. Thanks.

RE: Gypsum Roof Deck Diaphragm Shear

Try the www.NRDCA.org website. They have some info on gypsum-bulb tee roofs.  Not sure if they have technical data.
 

RE: Gypsum Roof Deck Diaphragm Shear

Ever since I can remember, it has been a BIG NO NO to use GSB at the roof or floor to resist any lateral loading as a structural diaphragm. I was trained that way. I have always used plywood, metal decking, X bracing, or concrete to do this.

Mike McCann
MMC Engineering

RE: Gypsum Roof Deck Diaphragm Shear

Poured, lightly reinforced, gypsum concrete decks on bulb tees were popular in the 60's and 70's.  In those days, we didn't bother much with diaphragm calculations, and I don't remember ever seeing any information on diaphragm capacity of gypsum decks.  Intuitively, it is a lot stiffer than a metal deck, provided the roof hasn't leaked.

RE: Gypsum Roof Deck Diaphragm Shear

Sorry.  I guess I misread...again.

Mike McCann
MMC Engineering

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