(1) Except as provided in Sentences (2) and (3), a building is permitted to be classified as not dynamically sensitive.
(2) A building shall be classified as dynamically sensitive if,
(a) its lowest natural frequency is less than 1 Hz and greater than 0.25 Hz,
(b) its height is greater than 60 m, or
(c) its height is greater than 4 times its minimum effective width considering all wind directions, where the effective width, w, of a building shall be taken as,
w = (Σ h_i w_i) / (Σ h_i)
where,
the summations are over the height of the building for a given wind direction,
hi =the height above grade to level i, and
wi =the width normal to the wind direction at height hi.
(3) A building shall be classified as very dynamically sensitive if,
(a) its lowest natural frequency is less than or equal to 0.25 Hz, or
(b) its height is more than 6 times its minimum effective width, where the minimum effective width is determined in accordance with Clause (2) (c).