PART 4 — STRUCTURAL DESIGNUpdated for the 2024 Ontario Building Code
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4.1.7.2.Classification of Buildings (See Note A-4.1.7.2.)
(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,
∑ hi wi
w =
∑ hi
where the summations are over the height of the building for a given wind direction, hi is the height above grade to
level i, and wi is the width normal to the wind direction at height hi; the minimum effective width is the lowest value
of the effective width considering all wind directions.
(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) it contains a human occupancy, and its height is more than 6 times its minimum effective width as defined in
Clause (2)(c).
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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.