Truss Cambering Tool

Last updated April 28, 2017 by Steel Extensions

Software version: 
Not environment-specific

Truss Cambering Tool


Purpose and description
System Requirements
Truss Cambering Tool settings
Additional information

Purpose and description

Once a truss is erected and subject to dead and working loads, its booms deflect into a resting position and the lacing members are either extended or compressed according to their situation. Trusses are therefore often fabricated with their booms pre-cambered and their lacings shortened or lengthened by a calculated distance in order that once in service they acheive their theoretical (required) shape.

Using this component, the user may create a pre-cambered truss from an existing truss in the model. The component allows the truss to be modeled in its theoretical (deflected) position, whilst having the output provide information and prepare the members so that the truss may be fabricated in a pre-cambered state.  

The component does this by taking user-specified camber values for the top and bottom booms and applying appropriate ‘Shorten’ UDAobject property created by the user in order to widen the range of predefined object properties

User-defined attributes are used when the predefined object properties are not sufficient but more properties are needed. For example, comment, locked, and erection status are user-defined attributes.

values to each lacing member connecting between booms. After a truss is cambered using this tool, the companion Truss Camberingdeforming that curves a part to compensate for deflection which arises due to loads on the structure

Cambering is typically an upward curvature defined for a beam.

Diagram plugincomponent that is developed using Tekla Open API

Plugin is a .dll file and loaded inside Tekla Structures process.

Plugins can be started from the applications and components catalog.

uses that information to add a cambering diagram to an assembly drawingdrawing that shows fabrication information for a basic or a nested assembly, including bolts and welds, and that is generally used at the workshop

Assembly drawings show how parts are located in an assembly. They contain the parts of the assembly presented in one or more views.

of the truss in order to assist the fabricator.

System requirements

Tekla Structures
.NET Framework version: 4.0
Environments:   Default


The extension is now available in two formats; Tekla Structures version (and x86/64bit) specific *.msi installers that support Tekla versions up to and including 21.1 and from Tekla Structures 2016 or later, a *.tsep (Tekla Structures extension package) format.

To install the *.msi based extensions to Tekla Structures 21.0 or earlier:

  1. Close Tekla Structures.
  2. Install the applicationpart of Tekla Structures functionality that is developed in order to extend the capability of Tekla Structures but that is not included in the Tekla Structures installation

    using the appropriate 32bit (x86) or 64bit installation package.

To install the *.tsep based extensions to Tekla Structures (available for Tekla Structures 2016 or later) from Tekla Warehouseservice for collaboration and for storing and sharing Tekla Structures content

In Tekla Warehouse the content items are stored in collections. Tekla Warehouse includes the Tekla Warehouse Service and the Tekla Warehouse web site.

Tekla Warehouse is one of the Tekla Online services.


  1. Download the extension from Tekla Warehouse.
  2. According to which browser you are using, when the file has been downloaded either the Tekla Structures extension manager will open automatically or you may need to right click on the downloaded file and choose the 'open' option.
  3. The Tekla Structures extension manager dialog will be displayed and will show a list of installed Tekla Structures versions compatible with the extension. Choose the versions you wish to install to by selecting the check boxes next to each version's name, then click 'Import'. You may be asked to accept the License.
  4. The extensions will now be queued for installation to the selected versions. The installation will happen the next time that version is started.

To install a saved *.tsep extension package to additional Tekla Structures installations.

Having downloaded a *.tsep based extension, that file may be saved and installed on multiple Tekla Structures installations:

  1. To import from a running Tekla Structures:
    1. Open the Applications & Components menu and from its 'Access advanced features' button menu select 'Extension manager...' which will open the manager dialog.
    2. Click on the 'Import...' button and browse to the extension you wish to install.
    3. The chosen extension will be added to the import queue for the running version and installed when Tekla Structures is next restarted.
  2. To install from the file manager menu:
    1. browse to the saved file, right click on the file and select 'Open', the Tekla Structures extension manager dialog will be displayed.
    2. Choose the version(s) to install to and click on 'Import'.
    3. The chosen extension will be added to the import queue for the version(s) selected and installed when Tekla Structures is next restarted.

Applications and Components menu

From Tekla Structures version 21.1 the extension is accessed from the Applications & components menu. The installer creates a group called Truss Cambering Tool extension' in the root folder with an icon for the extension component. If you wish to customise the menu, the component may be added to any new or existing groups in the normal way. To remove the automatically created Truss Cambering Tool extension group it is necessary to locate the catalog filefile that defines catalog information used by Tekla Structures

Catalog files can have different file name extensions, for example, .bin, .db, or .inp.

installed as part of this extension and remove it (this will also remove the descriptions of the components so you will need to provide your own). That file is located in the Environments\common\extensions\TrussCamberingTool folder and is called Note that renaming the .ac.xml part of the name will cause it to be ignored too.


To use the Truss Cambering Tool component:

For the tool to be used, it is assumed that the beams in the truss are already added to the model, and that all the neutral axes of these beams share a vertical plane (up to certain tolerances, which may be adjusted in the dialog.)  Each beam must be either part of the top boom, part of the bottom boom, or a lacing beam connecting the top boom to the bottom boom.

1. Open the Component Catalogcatalog that contains all system components and custom components, and the macros and applications

(Ctrl + F).
2. Either use 'Search' or browse the 'Plugins' category to find the Truss Cambering Tool extension.
3. Double-click on the icon to open the dialog and set the preferred parameters in the normal way. (Use 'Save As' to save defaults).
4. When it starts, the tool will prompt the user to select beams and points in the following order:

4.1. The beams making up the top boom.  When these are selected, press the middle mouse button or Enter.
4.2. The point at which the top boom camber, as specified in the dialog, should be applied.
4.3. The beams making up the bottom boom.  When these are selected, press the middle mouse button or Enter.
4.4. The point at which the bottom boom camber should be applied.
4.5. The lacing beams between the top and bottom: these are the beams that will receive the calculated Shorten UDAs.  When these are selected, press the middle mouse button or Enter.
At any time, the command may be terminated by pressing Esc or selecting Interrupt.

The easiest way to view the results is to use add Camber and Shorten UDAs to Part labels in model views:

(Remember to use the template names "cambering" and "xs_shorten" for these UDAs).

To change the camber values for a truss already cambered, double-click its component icon (or right-click and select Properties), edit the cambers, and click Modify.

Truss Cambering Tool settings

The dialog can be used to set the tool attributes.  These give the boom camber distances at the defined points, and tolerances that guard against unsuitable use.

Property Description
Top boom camber. At the top boom camber placement point, this is the distance that the top boom will drop.
Bottom boom camber. At the bottom boom camber placement point, this is the distance that the bottom boom will drop.
Boom out of 2D truss plane tolerance. If a neutral axis end point of a boom beam is greater than this distance from the vertical plane of the truss, an error is assumed.
Lacing end to boom tolerance. If a neutral axis end point of a lacing is greater than this distance from any boom beam, this will be assumed invalid as a lacing.
Maximum slope for camber UDA. A boom beam will receive a camber UDA only if its slope is less than this angle and is the only beam in the boom.  Otherwise the camber UDA is set blank.

Additional information

Calculation of lacing shortenings:

A standard approximation for estimating the drop distances along the length of a truss boom is that they follow a parabola.  The tool uses this method to estimate the drop distance of each lacing end.  From these, it calculates the length each lacing should be fabricated to, and from that suitable shorten values.

  • For both booms, the tool calculates
    • its solid extents,
    • the ratio along the boom of the camber placement point, and
    • the maximum camber.
  • For each lacing end point, the tool calculates
    • the ratio along the closest boom,
    • its drop distance, and
    • the point at which the erected lacing end would be.
  • The lacing shorten values is then the difference in lengths of the modelled beam and the erected beam.

Note also:

  • All lacings must connect the top boom to the bottom boom.  It does not handle spliced lacings.
  • If you do need to move a truss cambered with tool, the camber placement points will not move with the beams.  Suggestion: use "Save as" from the dialog, delete the component, and then apply the tool again.

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