The following error "The beam cannot form part of a braced frame" may appear over elements defined as "Beam" in CYPE 3D placed on the perimeter of a braced frame:
To avoid this error, the definition of these elements should be modified from "Bar", "Describe" and selecting the "Generic" structural element type at the top of the pop-up window, instead of a "Beam".
For more information, please check the following link to see the program's conditions for identifying a braced frame.