Output Mass Moment of Inertia (MMI) for wind tunnel study

[MPBNI]

Hi all,

I need to provide building information for a wind tunnel study. I have a rectangular concrete building with a hipped roof. One piece of information I need is the Mass Moment of Inertia (MMI) for each story. These numbers are easily accessed through File<Print tables<input, and then selecting "mass"; however the numbers are assigned to rigid diaphragms, and like I said, I have a hipped roof, which is not permitted to have a rigid diaphragm.

Are there any thoughts on how I might accurately get this information, despite not having a rigid diaphragm at the roof to attach the mass to?

Thanks.