In Ram Structural System 14.07 a change was made in the behavior of 2-way slabs under lateral loads. To prevent the slab from coupling lateral walls and columns together the out-of-plane stiffness is ignored in those lateral load cases when the diaphragm is set to rigid. With the out-of-plane stiffness near zero, the unbalanced forces in lateral columns above and below the slab are necessarily tiny.
In order to have the out of plane stiffness considered under lateral loads the diaphragm at the level being exported to Ram Concept must be set to semi-rigid.
RAMSS Two Way Decks
RAM Frame - Criteria - Diaphragms