Ancillaries

Tekla Structural Designer
2021
Tekla Structural Designer

Ancillaries

Ancillaries enable the quick and efficient application of loading from ancillary items such as ladders, stairs and pipework etc - that are not part of the main structural frame.

What are ancillaries used for?

While primarily intended for use in industrial structures, some features associated with ancillary loads are also beneficial to the AEC market - eg:
  • Modeling of stairs in steel, concrete, and timber structures,
  • The use of stairs in combination with inactive members.

Ancillaries can also be used to model loads from:

  • Walkways/Catwalks
  • Ladders (with/without cages)
  • Access Platforms
  • Operating Platforms (Storage/Standard)
  • Lines of Pipework
  • Lines of Cable Tray

In Tekla Structural Designer each of the above types can be created in the form of either a line, or area ancillary.

Line ancillaries

Line ancillaries can be defined horizontally, vertically or sloped. They are created by selecting a series of support points in order to create a "run". Each line has a defined width in a user defined plane (perpendicular to length).

Area ancillaries

Area ancillaries can be defined horizontally, vertically or sloped. They are created in the same way as a panel, by selecting the vertices of the area.

Ancillary load default values

Each Line or Area Ancillary has default Dead Loads and Imposed/Live Loads which can be preset to be project specific from the subpages under Loading in Model Settings.

The default values can be overridden when individual ancillaries are created.

Note: For Pipework Operating & Testing Content Loadcase Types, you can select whether these are considered as Dead or Imposed (Live) loads from Model Settings > Loading > General.

Ancillary loadcases

Ancillary loads are created in dedicated loadcases which are automatically added and removed as the loads are added/deleted. These dedicated loadcases specifically aid combination building for Industrial design.

Most types of ancillary load are created in the Ancillary Dead & Ancillary Live (Imposed) loadcases. The two exceptions are lines of pipework which are created in the Pipework Empty, Pipework Operating Content & Pipework Testing Content loadcases, and lines of cable tray which are created in the Cable Tray Empty & Cable Tray Content loadcases.

Note:

If working to Eurocodes, the ancillary imposed case Ψ and ɸ factors default to Ψ1 = 1.0, Ψ2 = 0.9, Ψ3 = 0.8, ɸ = 1.0.

Some ancillaries may require different values in which case a new imposed loadcase should be manually added with the desired Ψ and ɸ factors. Then when the ancillary load is being created the loads can be put into the new loadcase instead of the dedicated loadcase by changing the Imposed Load Loadcase in the Properties window from 'default' to that required.

Ancillary load decomposition

All decomposed loads from ancillaries are present in the analysis and design.

Once loads are decomposed the ancillaries themselves play no further part in analysis and design.

Line ancillary decomposition

Line ancillaries are treated as simply supported beams, spanning onto supporting members/slabs.

Decomposition is in two stages from the line ancillary to its supports then onwards.

In the below example the line ancillary is supported by a beam at one end and a slab spanning perpendicular to the ancillary at the other. At the slab end, stage 2 decomposition occurs to distribute the load on to beams supporting the slab.

Area ancillary decomposition

In the same way as a roof panel, an area ancillary has a span direction which determines the load decomposition onto surrounding supporting members/slabs.

Decomposition is in two stages from the area ancillary to its supports then onwards.

In the below example the area ancillary is supported by a slab which spans in the same direction as the ancillary.

The UDLs generated in the stage 1 decomposition are then decomposed on to the members supporting the slab in stage 2.

Create line ancillary loads

  1. On the Model tab, clickLine Ancillary.
  2. In the Properties window,
    1. If the load is to only span between two points, uncheck the Continuous setting, otherwise leave it checked.
    2. Enter the load width
    3. Select the required Type.
    4. Accept the default load values, or define your own.
    5. Specify the remaining properties as appropriate to selected Type.
      Note:
      1. For walkways and platforms the presence of a guardrail and channel height alters dead loading.
      2. For lines of pipework/cable trays the height is displayed and it can be visually reversed by checking the Reversed property.

  3. Click the start point of the line.
  4. Click the remaining points of the line.
  5. Double-click to define the end point of the line.
  6. Pick a reference point to define the ancillary plane.

    Tekla Structural Designer creates a line ancillary between the selected points.

Create area ancillary loads

  1. On the Model tab, clickArea Ancillary.
  2. In the Properties window,
    1. The rotation angle defines the span direction measured relative to the first two points clicked to identify the area.
    2. Select the required Type.
    3. Accept the default load values, or define your own.
    4. Specify the remaining properties as appropriate to selected Type.
      Note:
      1. For walkways and platforms the presence of a guardrail and channel height alters dead loading.
      2. For lines of pipework/cable trays the height is displayed and it can be visually reversed by checking the Reversed property.

  3. Click the start point of the area.
  4. Click the remaining points of the area.
  5. To define the end point of the area, do one of the following:
    • Double-click the end point.

    • Click the end point, and click the start point again.

    Tekla Structural Designer creates an area ancillary load between the selected points.

Generate ancillary combinations

You can generate combinations automatically in the normal way, however if you have created pipework or cable tray loadcases you may need to make use of combination 'scenarios' to prevent the empty and content loadcases from being included in the same combination. The steps for doing this for pipework loadcases are illustrated below (cable tray loadcases being similar):
  1. On the Load tab, click Loadcases.

    The Loading dialog box opens on the Loadcases page. On this page, you can see the loadcases that have been created and select which ones are to include when combinations are generated.

  2. To generate combination(s) for the pipework empty loadcase, check 'Include in Generator' for Pipework Empty but uncheck the other pipework loadcases.
  3. At the top of the dialog, click Combinations.
  4. Click Generate.
  5. In the Combination Generator, enter an appropriate name for the 'empty' scenario and select the Replace only combinations generated by this run option.
  6. Make appropriate selections to generate the combination(s) required for this scenario, then click Finish to see the result.
  7. Click Loadcases to return to the Loadcases page.
  8. Check 'Include in Generator' for Pipework Operating Content but uncheck the other equipment loadcases.
  9. On the Combinations page, click Generate.
  10. In the Combination Generator, enter an appropriate name for the 'operating' scenario and select the Replace only combinations generated by this run option.
  11. Make appropriate selections to generate the combination(s) required for this scenario, then click Finish to see the result.
  12. On the Loadcases page, check 'Include in Generator' for Pipework Testing Content but uncheck the other pipework loadcases.
  13. On the Combinations page, click Generate.
  14. In the Combination Generator, enter an appropriate name for the 'testing' scenario and select the Replace only combinations generated by this run option.
  15. Make appropriate selections to generate the combination(s) required for this scenario, then click Finish to see the result.
  16. Click OK

Create an ancillary loads report

A table of the ancillary loads applied to the model is available in the Industrial Structure Loading report, which is created as follows:

  1. On the ribbon, go to the Report tab.
  2. In the list on the left side, select Industrial Structure Loading.
  3. Click Show Report.
    Tip: If the resulting report displays too little or too much information, adjust the content by re-configuring the report.
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