ASCE Diaphragm Discontinuity Irregularity
Diaphragm discontinuity irregularity is defined to exist where there is a diaphragm with a cut or open area grater than 50% of the gross diaphragm area or a sudden break or variation in stiffness, in effective diaphragm stiffness of more than 50%.
In buildings with type 3 irregularity, story slabs is modeled with two-dimensional plate (membrane) or shell finite elements to show that they are able to safely transfer earthquake forces between vertical bearing system elements in their own planes.
In buildings where there is type 3 irregularity and / or story floors are not intended to operate as a rigid diaphragm, and in flat slabs, story floors are modeled with two-dimensional finite elements.
