Where are the missing mass mode in individual Modal results in AutoPIPE's output report?
How to print the Missing mass mode for MSRS.
At this time, Missing Mass contribution are not printed in the modal report.
One way to find the contribution of missing mass could to be see the difference between two response spectrum cases (one with and other without Missing mass option checked) in the OUT report.
Dynamic "Response Spectrum" Analysis
Bentley AutoPIPE