Unblocked Diaphragms

[openam]

I have a diaphram that is seperated with 1' gaps, see diagram. I'm trying to decide if this could be considered an unblocked diaphragm. It seems that the shear would have to transfer through the trusses just as it would in an unblocked diaphragm. I know that they require a gap in unblocked diaphragms, but is it ok for this gap to be 1' wide? Does anyone know where to point me to figure out if this is acceptable?

x dimension = 60'
y dimension = 170'
trusses run in the x direction and are placed at 4' O.C.


1' 1' 1'
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y

 

[AlohaBob]

When you have such gaps, the panels don't act like a diaphram - blocked or unblocked. It would act like independent diaphrams connected by beams - weak axis bending in the roof members to link the independent diaphrams, or struts to share loads with 4 diaphrams in the perpendicular direction. The long axis stiffness is nearly naught in plane. The analysis would be rigorous to qualify this for providing stability to your system. It looks like your diaphram aspect ratio is too high to even formally qualify the subdiaphrams.

You might consider using a brace system in the roof plane rather than go the diaphram route.