The sway check

Note: The sway check is not relevant to models that use the ACI/AISC head code.

By default the sway check is applied to all columns (of all materials), and all walls.

Sway check design options

In Design Settings > Sway & Drift Checks, there is a Merge short stacks option (default Off) that applies to the check as follows:

With the setting Off, the check considers all stacks of all columns/walls apart from those that have been manually excluded.
With the setting On, any stacks that are less than the limit specified are merged with the stack below, and the check is performed on the merged stack length. The check is not performed on single stack columns/walls that are less than this limit

Manually exclude an entire column or wall or an individual column stack or wall panel from the check

An entire column/wall can be excluded from the check by unselecting Sway/Seismic drift checks located under All stacks/panels>Sway and drift checks in the column/wall properties window.

Similarly an individual stack/panel can be excluded from the check by unselecting Sway/Seismic drift checks located under Sway and drift checks for the specific stack/panel in the column/wall properties window.

Manually adjust automatically determined stack lengths

Columns are divided into stacks and walls are divided into panels at floor levels where members or slabs connect to the column/wall. For the purposes of Sway/Drift, Wind Drift and Seismic Drift checks only you can override the default stack/panel divisions by merging a stack/panel with a lower stack/panel. The length of the combined stack/panel is then used in the checks.

In order to do this you would have to select Merge with stack below located under Sway and Drift Checks for the specific stack/panel in the column/wall properties window.

Perform sway checks

The checks are performed either by running Analyse All (Static) from the Analyse ribbon, or by running any of the Design (Gravity), or Design (Static) commands from the Design ribbon.

Note:

For non-linear models with Tension Only bracing it is essential that the 'X Brace' pattern is used to input the braces as brace pairs rather than creating them individually. For linear analysis one of the braces in a brace pair is automatically inactivated, ensuring that the model's lateral stiffness, and hence lateral drift, is reasonably correct. If braces are input individually this will not be the case.

For those stacks to which the check has been applied, the storey drift in each direction (i.e. the difference between top and bottom deflection of the stack) is calculated, and from this the elastic critical load factor is determined.

Review sway checks

For those stacks to which the check has been applied the elastic critical load factor is calculated in both directions, and the building's overall sway check status is displayed in the Design branch of the Status Tree in the Project Workspace.

Any column in this branch with a warning status can be double clicked on in order to highlight it in amber in the current view.
Double click on the Sway main heading in order to highlight all columns with warnings in amber

Note:

Sway warnings remain highlighted in the current view until you press Esc to clear the highlight.

In addition to viewing the summary in the Project Workspace, the sway checks can be interrogated in a variety of ways:

To display sway values on the structure, see Display sway drift and story shear
To review/modify the checks graphically, see Review and modify sway checks
To review the detailed checks in a table, see Review sway check tabular results

Report sway checks

If required, the sway results table can be included in printed output by adding the Analysis>Sway chapter to your model report.

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