2 separate response spectrum under 2 load cases

Hello Community,

I have small doubt about the response spectrum mass definition.

Is it possible to define 2 different response spectrum in single model / STAAD file.

I am designing structure for number of fluid tanks, which may be either filled or empty depending on their operation.

So I want to define 2 separate response spectrum with flooded weight (Fluid weight + empty weight) of tank and other response spectrum with empty weight of tanks respectively.

So is it possible to define the 2 separate response spectrum in same STAAD file?

Please share your opinion.

Thank you.