B2 irregularity checks are made automatically and detailed results are given in the Earthquake Regulation report.
h i = height of the i'th storey
Δ i (x) = (X) for any column or curtain in the earthquake direction, reduced relative storey displacement expressing the displacement difference between two consecutive floors
η ki = Stiffness Irregularity Coefficient defined at the i'th storey
B2, Stiffness Irregularity Between Neighboring Stories, Stiffness Irregularity Coefficient η, which is defined by dividing the average relative storey drift ratio in any i'th storey by the average relative storey displacement ratio of the upper or lower storey for any of the two earthquake directions perpendicular to each other, excluding basements. Where ki is greater than 2.0.
η ki = (Δ i (X) / h i ) ort / (Δ i + 1 (X) / h i + 1 ) ort > 2.0 or
η ki = (Δ i (X) / h i ) ort / (Δ i-1(X)/hi-1)ort > 2.0
This type of irregularity affects the Selection of Linear Calculation Method described in Section 4.6 of TBDY . According to Table 4.4 , if the Torsional Irregularity Coefficient η bi value is less than 2, the Equivalent Earthquake Load Method can be used. However, ideCAD Static TBDY uses the Modal Calculation Methods and Linear Earthquake Calculation specified in Section 4.8 ( Modal Response Spectrum Analysis andMode Addition Method in Time Domain ). Therefore, if the building contains B2 type irregularities,Modal Calculation Methods and Linear Earthquake Calculation according to 188.8.131.52 are valid.
According to Table 3.6 , the calculation of the relative storey drifts is made according to the Equivalent Earthquake Load Method described in Section 4.7 of TBDY, taking into account the effects of + - 5% eccentricity . While Modal Calculation Methods are used in the earthquake calculation of the building, Equivalent Earthquake Load Method is used in B2 type irregularity control.