The Ontario Building Code | Dynamic Effects of Wind
4.1.7.2. Dynamic Effects of Wind
(1) Except as provided in Sentence (2), buildings whose height is greater than 4 times their minimum effective width, which is defined in Sentence (3), or greater than 60 m and buildings whose lowest natural frequency is less than 1 Hz, as determined by rational analysis, shall be designed by,
(a) experimental methods for the danger of dynamic overloading, vibration and the effects of fatigue, or
(b) using a dynamic approach to the action of wind gusts.
(2) Buildings whose lowest natural frequency is less than 1/4 Hz, as determined by rational analysis, shall be designed by experimental methods in accordance with Clause (1) (a).
(3) The effective width, w, of a building shall be calculated using the formula,
where,
the summations are over the height of the building for a given wind direction,
hi is the height above grade to level i, as defined in Sentence 4.1.7.1.(5),
wi is the width normal to the wind direction at height hi, and
the minimum effective width is the lowest value of the effective width considering all possible wind directions.