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For Seismic Design Categories D, E and F, ASCE 7 12.3.3.4 requires an increase of 25% in drag strut forces for structures that have any of the horizontal irregularities 1-4 from table 12.3-1. or which have vertical irregularity 4 from table 12.3.2. Noting that horizontal irregularity 5 cannot occur in Shearwalls, the increase is applied of you select any horizontal irregularity or vertical irregularity 4 in the Site Dialog. Torsional Irregularities 1a and 1b apply only to rigid diaphragm design.
The 25% increase is also applied if on the level above the drag strut, there is a shear line in that direction with no line on the level below ( Horizontal Irregularity 4 - Out of Plane Offset), regardless of the setting of 2 Corner, 3 Diaphragm or 4 Offset In the Site Dialog.