Gypsum Roof Deck Diaphragm Shear

[w16x26]

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.

 

[MiketheEngineer]

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

 

[w16x26]

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.

 

[lsmfse]

Try the

http://www.NRDCA.org

website. They have some info on gypsum-bulb tee roofs. Not sure if they have technical data.

 

[msquared48]

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

 

[hokie66]

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.

 

[msquared48]

Sorry. I guess I misread...again.

Mike McCann
MMC Engineering