This chapter explains the theoretical background of couplings with the "rigid diaphragm" story slab stiffness. This type uses the objects of the "rigid link" type. They are described in Chapter Rigid Links of the RFEM manual.
The "rigid diaphragm" story slab stiffness is used to connect all components of a story – members, surfaces, and solids – in the plane of the upper point of the story slab with a rigid link. The connection is made in the center of gravity of the story. The governing criterion for this is thus the weight of the individual connected components. Therefore, a very heavy member on one side of a story shifts the center of gravity in the corresponding direction.
In the following model, there are relatively light timber members on one side of the second floor. This moves the center of gravity to the other side of the floor.
