Buidling Period
Notes:
1- This module adopts free vibration theory formulae for fundamental frequencies
2- Effective Section is most important, for example if ETABS section modifier for cores
is at 0.4, this does not mean the inertia of a core is reduced by 60%, because we are dealing
in this case with a box where the inertia relates to transformed inertias of individual components
of the core. Use judgement when dealing with such situations.
It becomes straightforward in case of single walls
3- Note the core inertia is also reduced in case of coupeling beams, make an allowance for this