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Maximum Plan Offset
The maximum separation between parallel walls on the same building level for those walls to be along the same shear line (i.e. subject to the same loads and part of the same resisting system).
The CSA O86 and does not deal with plan offsets, but a value of 150 mm is recommended to provide tolerance for the automatic shear line generation routine.
Maximum Elevation Offset
The maximum separation between parallel walls on the different building levels for those walls to be along the same shear line (i.e. subject to the same loads and part of the same resisting system). The CSA O86 and NBC do not deal with elevation offsets.
The elevation offset must not be considerably larger than the plan offset, or the program will not behave in a predictable manner. However, an elevation offset smaller than the plan offset effectively reduces the plan offset to the smaller value for those walls that line up vertically. That is, a small inset wall 6" away from a parallel wall be on the same shear line for one-story buildings with a 6"maximum offset, but if the elevation offset is less than 6", the program will place it on a different shear line, because it can't be on the same shear line as the offset wall on the level above.
Elevation offsets are measured in joist depths. The default value is one joist depth, creating an offset slightly larger than the default plan offset for the default floor joist size of 10".