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1a. Torsional Irregularity: The case where Torsional Irregularity Factor, which is defined for any of the two orthogonal earthquake directions as the ratio of the maximum story drift at any story to the average relative story drifts at the same story in the same direction, is greater than 1.2. Maximum story drift, computed including accidental torsion with A_x =1.0. Torsional irregularity requirements in the reference sections apply only to structures in which the diaphragms are rigid or semirigid.

1b. Extreme Torsional Irregularity: The case where Torsional Irregularity Factor, which is defined for any of the two orthogonal earthquake directions as the ratio of the maximum story drift at any story to the average relative story drifts at the same story in the same direction, is greater than 1.2. Maximum story drift, computed including accidental torsion with A_x =1.0. Extreme Torsional irregularity requirements in the reference sections apply only to structures in which the diaphragms are rigid or semirigid.

2. Reentrant Corner Irregularity: The cases where dimensions of projections in both of the two perpendicular directions in plan exceed the total plan dimensions of that story of the building in the respective directions by more than 15%

3. Diaphragm Discontinuity Irregularity: The cases where there is a diaphragm with an abrupt discontinuity or variation in stiffness, including those with a cut-off or open area greater than 50% of the gross closed diaphragm area, more than 50% effective diaphragm stiffness change from one story to the next.

4. Out-of-Plane Offset Irregularity: The casewhere there is a lateral force-resistance path discontinuity, such as an out-of-plane offset of the vertical elements.

5. Nonparallel System Irregularity: The case where lateral force-resisting elements are not parallel to the major orthogonal axes of the seismic force-resisting system.