For the most part, there is one envelope curve shared between storeys with the same cross section… with one exception!
We all encounter deep, philosophical questions that shake us to the very core. It has been estimated that masonry shear wall P-M Diagrams are one of the lagging causes of existential dread.
Disclaimer: This post is exclusively intended to provide insight into the approach taken by the MASS design software in interpreting a CSA S304-14 code compliant seismic design. It is up to the professional discretion of the designer to input an appropriate layout, boundary and loading conditions, interpret the results, and determine how they should be incorporated into their designs. As per the end user license agreement (and also recommended within PEO’s guidelines for using engineering software), a tool cannot be considered competent and reliance on a tool does not relieve the user of responsibility.
The video embedded below explains my thought process in looking at the case where each floor shares a designed cross section yet different envelope curves are plotted on the P-M Diagram.
Hopefully this quickly answers your question and explains this interesting design scenario. If you have any further questions, please do not hesitate to contact MASS support.