Story Drift

Hi,

I'm trying to assess the story drift for a building with a flexible diaphragm roof and rigid diaphragm floors using STAAD Pro v8i.

I modeled the rigid diaphragms using the Floor Diaphragm option but did not include the roof diaphragm in the model.

However, when I use the PRINT STORY DRIFT command, the drifts at the roof level doesn't show.

What is causing this problem and how can this be resolved?

Kind Regards,

Justin Redman