horizontal diaphragm single story residential sloped roof

[mjl23]

I'm new to residential design. If designing a single story structure (say residential) that has masonry or wood framed walls with wood trusses, what is assumed for the horizontal diaphragm? Most literature I have seen uses examples of plywood/OSB diaphragms in the horizontal direction. In this case, there would be plywood roof decking on top of wood trusses, and then the drywall attached to the bottom chord of the trusses for the ceiling. Wood the "roof" be assumed as a flexible (instead of rigid) diaphragm and the lateral forces just be distributed to the shear walls based on tributary area?

 

[DaveAtkins]

Yes.

DaveAtkins

 

[whyun]

http://www.seaint.org/seaocconvention/convention1999/Proceedings/panelreport.htm

This is a link to discussions related to rigid vs. flexible wood diaphragms (a bit dated).

I do not have the IBC definition but UBC definition of a flexible diaphragm is where you have diaphragm deflection is greater than twice the average story drift. Typically in residential construction, diaphragm lengths are relatively short. Almost all of the time, diaphragms will end up being flexible.

 

[msquared48]

The 2006 IBC reference for the requirements for the assumption of a flexible diaphragm can be found in section 1613.6, which also refers to section 12.3.1.1. of ASCE 7.