ASCE 1a and 1b- Torsional Irregularities

SYMBOLS

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

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1a - Torsion Irregularity

The Torsional Irregularity is defined to express the ratio of the maximum story drift, computed including accidental torsion with A_x =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.

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

Extreme Torsional Irregularity:

Extreme torsional irregularity is defined to express the ratio of the maximum story drift, computed including accidental torsion with A_x =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 storey displacements is made according to equivalent lateral force analysis, taking into account the ± 5% additional eccentricity effects.