The diaphragm is meshed if a two-way deck is found inside a diaphragm. Note that the diaphragm type can be rigid or semirigid. The program locks the diaphragm for lateral analysis if it is a rigid diaphragm. Hence,

• A two-way load distribution is considered for gravity loads. This is accomplished by out-of-plane (bending) stiffness of the diaphragm
• For lateral analysis, the diaphragm is locked: the diaphragm in-plane stiffness is represented with 3 degrees of freedom (translations in X and Y directions and rotation around Z-axis).

This procedure is automated and transparent to the user.