Curved Roof Diaphragm

[CENAEN]

I am currently designing a building with bowstring steel joists for the roof. I have a question regarding the design of the diaphragm in the direction of the curve (i.e. lateral load is along the curve). Is a curved diaphragm stiff enough to resist the lateral loads? I see the bottom chords being stiffner (adequately braced) than curved roof. Should I design the bottom chords as a diaphragm or should I use roarke's formulas to determine the shear along the joist's curve? Your thoughts.

This is our first experience with curved diaphragms and we haven't found too much info, any insight is appreciated.

Thanks for your time,
Juan

 

[pmkPE]

I am not sure I understand your "predicament"? The lateral forces from the top chords will be counterbalanced by the bottom chords in tension. Diaphragms are used to transfer the shears to the supporting members/structure. What forces are you trying to restrain? and where?

 

[AlohaBob]

I built a cement plant recently with a curved roof. I did some analysis on perpendicular roof loading, but I designed the building with rigid frames at spacings that limited roof shear. I used roof bracing to carry the lateral load, so a curved panel analysis didn't really apply to the barrel. Panel stresses are redundant. This way, you can hedge your bets as far as reliability issues with non-standard construction applications for structural purposes. The brace connections still look conventional. This may help you with conceptual design.