Horizontal irregularity (Torsional Irregularity)

[KenStructural]

Based on my experience the first 3 mode shapes of the structure should be translation into two orthogonal directions and 3rd is rotation, my question is in determining the structure if it has horizontal irregularity due to torsional irregularity the displacement is due to mode 3 (rotation) or the displacement describe per ASCE is the modal combination of translation and rotation. I'm attaching here the ASCE code requirements for reference. Any reply is appreciated

 

[JoshPlumSE]

No, this determination for whether a structure has a horizontal irregularity is independent of the torsional mode shape.

If you run an analysis using equivalent static loads (including accidental torsion if applicable)and you see that your structure is torque-ing under that applied load then you use these deflections to determine if you have a horizontal irregularity or not.