BNBC 2006 reference section

1) Tortinal irregularity

Torsional irregularity shall be considered to exist when the maximum story drift, computed including accidental torsion, at one end of the structure transverse to an axis is more than 1.2 times the average of the story drifts of the two ends of the structure.,,,

2) Re-entrant corners

Plan configuration of a structure and its lateral force resisting system contains re-entrant corners, where both projections of a structure beyond a re-entrant corner are greater than 15% of the plan dimension in the given direction.

3) Diaphragm discontinuity

Diaphragms with abrupt discontinuities or variations in stiffness, including those having cutout or open areas greater than 50% of the gross enclosed area of the diaphragm or changes in effective diaphragm stiffness of more than 50% from one story to the next.

4) Out-of-plane offsets

Discontinuities in a lateral force path, such as out-of-plane offsets of the vertical element.


5) Nonparallel systems

The vertical lateral load-resisting elements are no parallel to or symmetric about the major orthogonal axes of the lateral force-resisting system.