There is no problem in terms of program structure. You can do both. If you intend to separate them from the whole, including the fundamentals, it is easier to model them separately and solve them as a separate project. If you are going to do the basics as a whole, maybe data entry can be considered together. ( If you want, you can solve the structure separately and get the basic effects[/b][/u] command and you can give the loads of the other building) When you separate it from the dilatated areas and solve it in a single file, naturally more than one rigid diaphragm will occur.There are difficulties with naming here. The difficulty is as I said; the program gives a different name for each different rigid diaphragm. In this case, especially in the 2nd, 3rd basements or higher floors, the naming becomes longer and it is difficult to understand (especially for the masters). To give an example. There are 3 sections and each Let the names of the rigid diaphragm sections be A, B, C. For example, in the basement elements of Bblock 2, the nomenclature would be: Beams: KB2B117, KB2B118... Columns: SB2B117, SB2B118... Slabs: DB2B117, DB2B118... I recommend modeling them separately for reasons such as naming, layout design, etc.