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Home > User Interface > Analyses > Calculation Parameters > Pretension and Top Angle Requests

Pretension and angle requests

These options may be used to specify target values for the top tension or vertical angle at any connection point in a line. The length of the first element in the line will be automatically adjusted until the target value is reached.

Each request may be created by clicking the Add pretension request or Add initial angle request button. Each new request appears as a row with several input cells to be completed :

  • Object: select the line on which your request will apply from the drop down list.

  • Location: select a connection point in the line

  • Pretension or Initial angle: input the target value for the pretension (in N) or the initial vertical angle (in degrees)

  • Tolerance: sets the acceptable error on the tension or angle required. Standard value to use by default is 1e-03.

  • Iterations: sets the maximum number of iterations within the algorithm used to reach the target values. Standard value to use by default is 20.

    Note

    Pretension and initial angle requests are naturally mutually exclusive. You can not ask for a target pretension and initial angle at the same connection point.

The FE engine automatically adapts the length of the first element in the line that is located next to the connection point where the target tension or angle is requested. The length of the first element is allowed to vary from zero to twice the initial length of the element. This means that the target value might not be reached in the event this would require significant changes in the length larger than twice the original length of the first element.

The FE engine reports in the DAY file whether the requested target tension or angle is achieved. An example of output that is reported in the DAY file is shown below:

In case the target value cannot not reached, you should either:

  • change the total length of the line so as to get initial tension or angle closer to the target value

  • use a coarser mesh with increased length for the first element so as to increase the range of tension or angle that can be achieved when adapting the length of the first element between zero and twice the initial length of the element.

Once the target tension or angle is found, you must set the correct adapted length in the Line data form.

Warning

Post-processing of tension at the connection point with the user interface may report incorrect values in case the adapted length was not set in the Line data form. This is because the FE engine had to adapt the length of the first element but does not pass the information to the user interface. The user interface would then consider that this element experiences significant axial strain and eventually report incorrect tension.

Other outputs such as reaction force recorded at the end node of the line however remain correct since they are calculated by the FE engine and reported in the DTBSR binary file which is in turn opened by the user interface during post-processing.