The Ontario Building Code | Direction of Loading
4.1.8.8. Direction of Loading
(1) Earthquake forces shall be assumed to act in any horizontal direction, except that the following shall be considered to provide adequate design force levels in the structure:
(a) where components of the SFRS are oriented along a set of orthogonal axes, independent analyses about each of the principal axes of the structure shall be performed,
(b) where the components of the SFRS are not oriented along a set of orthogonal axes and IEFaSa(0.2) is less than 0.35, independent analyses about any two orthogonal axes is permitted, or
(c) where the components of the SFRS are not oriented along a set of orthogonal axes and IEFaSa(0.2) is equal to or greater than 0.35, analysis of the structure independently in any two orthogonal directions for 100% of the prescribed earthquake loads applied in one direction plus 30% of the prescribed earthquake loads in the perpendicular direction, with the combination requiring the greater element strength being used in the design.
In Plain Language
Earthquake forces are assumed to act in any horizontal direction, though this article specifies particular loading directions that must be considered to ensure the seismic design force levels are adequate.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.