Modelling of 25 storey building with the specified properties using ETABS

Result:- 1) Fundamental Translational natural period

X-Direction 3.37Sec

Y-Direction 3.22sec

2) Torsional Irregularity

Yes

3) Vertical Irregularity

i) First three modes together should contribute at least 65% in Mass Participation Factor in each Principal direction

Modal 1- 3.372sec

Modal 2- 3.225sec

Modal 3- 2.51sec

ii) Fundamental lateral natural period in two Principal plane directiom are away from each other by at least 10%

- From Modal Participating Mass Ratio table

The period of Modal 1= 3.372sec

= 3.372*0.9 = 3.034sec which is less than 3.225sec i.e, modal 3

4) Inter-Storey drift