1a and 1b Torsional Irregularities per ASCE 7-16

SYMBOLS

Δ_avg = Average reduced relative story displacement on i'th floor of the building
Δ_max = Maximum reduced relative story displacement on i'th story of the building
Δ_min = Minimum reduced relative story displacement on i'th story of the building

1a - Torsion Irregularity

The Torsional Irregularity is defined to express the ratio of the maximum story drift, computed including accidental torsion with Ax =1.0, to the average relative story drift at the same direction is greater than 1.2. Torsional irregularity requirements in the reference sections apply only to structures in which the diaphragms are rigid or semirigid.

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The calculation of the relative story displacements is made according to equivalent lateral force analysis, taking into account the ± 5% additional eccentricity effects.

1b - Extreme Torsional Irregularity:

Extreme torsional irregularity is defined to express the ratio of the maximum story drift, computed including accidental torsion with Ax =1.0, to the average relative story drift at the same direction is greater than 1.4. Extreme torsional irregularity requirements in the reference sections apply only to structures in which the diaphragms are rigid or semirigid.
The calculation of the relative story displacements is made according to equivalent lateral force analysis, taking into account the ± 5% additional eccentricity effects.