Wind drift check

Tekla Structural Designer
Tekla Structural Designer

Wind drift check

By default this check is applied to all columns (of all materials), and all walls at every level in the model.

Results are presented in terms of levels, with detailed results for individual column/wall stacks/panels also being available.

For levels set as floors a Reporting Level option is displayed in Level Properties. By unselecting this option, individual levels can be excluded from the check reporting.

In this check the lateral drift resulting from the analysis is determined for each wind load combination using the combination SLS (Service Level) factors - (which can be < 1.0). This is then compared against a user-defined limit.

A workflow for running the check is outlined below:

Configure the check and set the limit

The check is configured from Design Settings.

On the Drift Checks page (if working to the ACI/AISC head code) or Sway & Drift Checks page (if working to any other head code) you can enter the limit required.

Note: By default the limit is set as 1/300 of the story height, in line with Eurocode 3 recommendations.

Individual limits can also be applied as overrides to selected stacks if required.

By default the check is performed in the resultant wind drift direction only, but by unselecting Check for Resultant Wind Drift it can be performed in each of Building Directions 1 & 2 if required.

By default the check only considers the effects of the wind loadcase(s) in wind combinations, but by unselecting Check wind cases only it will consider the effects of all loadcases in wind combinations (which would include drift induced by gravity loads).

Run the check

Wind load combinations are automatically checked on a level by level basis for wind drift during the structure static design, and also when any 3D analysis is run in isolation. If a sub-set of combinations are considered for analysis then only those combinations are considered in the wind drift checks, (allowing engineers working on larger structures to investigate and optimize the lateral load resisting systems more rapidly).

Review the check status and details

Once the check has been run, an overall status is reported in the Design branch of the Status Tree, the overall status being the worst status from each of the individual levels.

Right clicking on the status opens a context menu.
From this menu you can display the wind drift check summary in a Review Data Table, an example of this table for a Eurocode model is shown below.
By unselecting the above Summary Only option in the ribbon, the table can also display detailed results on a stack by stack basis if required.
The individual checks can be investigated in more detail by clicking the Details button at the end of any row.

Review the check graphically

From the right click menu in the Status Tree you are also provided with an option to graphically review the checks in a Show/Alter State View.

This color coded legend makes it easy to see individual failing members. By hovering the cursor over a member, its wind drift results are displayed in the tooltip.

From the same Show/Alter State view, by changing the Mode in the Properties window, you also have options to switch off checks, or set a different drift limit for specific stacks if you require.

Switching off inappropriate checks and merging stack lengths

After reviewing you might choose to switch off checks for selected columns and walls, or individual stacks/panels within selected columns and walls: this can be done directly via the Properties window, or graphically in a Show/Alter State view (as described in the previous section).

You might also choose to take advantage of the option to merge short stacks automatically where they are less than a specified limit. Stacks check lengths can also be be manually adjusted by merging them together if required.

An option is also provided which allows you to switch off checks for specific levels if you decide they are inappropriate, (for example if the story height is very short). The checks at that level are still performed, but they are excluded from the tabular review data display.

Printing calculations

The wind drift check results table is available either by creating a Building Analysis & Drift Checks report, or by including the Analysis>Wind Drift chapter in a custom report.

Note: The Wind Drift chapter has a Settings option that can be used to dramatically reduce the number of report pages. By default all columns and walls are output, but you can specify instead the most critical 'XX' columns and walls, (where 'XX' is a number of your choice).

The same Settings option also allows you to choose between reporting only the critical stack/all stacks, and reporting only the critical combination/all combinations.

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