Answer:
If you want to model stiffening walls in your structural system, you can do this using members of the Rigid member and Coupling types. To simulate a stiffening slab, you can model a diagonal member (or two) that simulates the surface.
If two nodes are connected by a coupling, this means that the internal forces are transferred directly from node to node. There are no "losses", as the members have infinite stiffness.
You can assign any hinges to the "Rigid member" type. There are four coupling variants with and without hinges.
More precise modeling is possible using FEA software RFEM, since the beam model only approximates the effects of walls and slabs. For example, you could create a beam model in RSTAB, then open it as a copy in RFEM to add the surface elements.
