A new feature has been added to easily model a rigid floor diaphragm without the need to specify a control joint at each. When specified, this command directs the engine to perform the following:

1. Calculate the center of mass for each rigid diaphragm (where control joint is to be located) considering the mass model of the structure. The mass must be modeled using mass reference load. See TR.31.6 Defining Reference Load Types
2. Create, internally, an analytical node at the center of mass location to be included during analysis (unless a control node is specified) if an existing analytical node exists at this point, then the existing joint is used in lieu of creating a new joint.
   Tip: The center of mass of each diaphragm is included in the preprocessing output. To include the center of rigidity in the post-processing output, you must include the PRINT DIAPHRAGM CR command. See TR.42 Print Specifications
3. Search all nodes available within a diaphragm and add them as dependent nodes; with the control node located at the center of mass for the diaphragm (or at the specified control node)