In order to understand the interaction between plates and members it is important that you know the basics of Physical Members and Plate Connectivity.

RISA-3D does not inherently have the capability to define a semi-rigid diaphragm. If you’re dealing with a complex roof system then you probably need to be able to model something that behaves accurately though.

To best understand how plates interact with each other you must first understand the concept of Physical Members. The important thing to keep in mind is that plates are not physical members.