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Define unfolding parameters in the unfold_corner_ratios.inp file

Last updated March 12, 2019 by Tekla User Assistance tekla.documentation@trimble.com

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Define unfolding parameters in the unfold_corner_ratios.inp file

Define unfolding parameters in the unfold_corner_ratios.inp file

The unfolding parameters define the location of the neutral axis when a profile is unfolded. The neutral axis is a line which runs along the length of a profile where stress and strain are equal to zero. Tekla Structures uses these parameters to create NC files and to display unfolded profiles in single-part drawings.

To define unfolding parameters, modify the unfold_corner_ratios.inp file, located in ..\ProgramData\Trimble\Tekla Structures\<version>\environments\common\system , using a standard text editor. You can copy the unfold_corner_ratios.inp file to a model, project or firm folderfolder that is used for storing Tekla Structures-related files customized for a particular organization

A Tekla Structures user can, for example, customize a company’s cloning templates and save them in a sub-folder located under the firm folder. After this, the customized cloning templates can be used in all projects carried out for the company.

and then modify the file in the new location as required. Tekla Structures searches for this file in the default search order.

After modifying the unfold_corner_ratios.inp file, restart Tekla Structures for the changes to take effect.


The settings in the unfold_corner_ratios.inp file have no effect in the following cases:

Unfold parameter properties

See below for an example of unfolding parameters in the unfold_corner_ratios.inp file and the descriptions of the parameters.

1 HE300A S235JR 0 180 2 0 1000 .7


In the example




1 is polybeams

2 is plates modeled as polybeams (for example, PLT)

3 is for parts which are not unfolded and follow the old polybeam calculation (for example, the line 3 L* * disables unfolding of L profiles)



You can also use wildcards with profile, for example, HE300*.



You can also use wildcards with material, for example, S235*.

Rotation / thickness min


For polybeams: the minimum angle when the profile is rotated around its longitudinal axis

For plates: the minimum thickness of plate

Rotation / thickness max


For polybeams: the maximum angle when the profile is rotated around its longitudinal axis

For plates: the maximum thickness of plate



This property defines what kind of parts are affected by the next two properties.

1 is sharp folds. Only polybeams with straight chamfers are affected.

2 is curved bends. Only polybeams with curved chamfers are affected.

Angle / radius min


For sharp folds: the minimum angle

For curved bends: the minimum radius

Angle / radius max


For sharp folds: the maximum angle

For curved bends: the maximum radius



Defines how much the profile stretches or shrinks when unfolded.

Ratio = (1 - the relative location of the neutral axis).

If only the inner surface of the profile shrinks, the ratio is 1. If only the outer surface of the profile stretches, the ratio is 0. By default, the ratio is 0.5 for length calculation and 0.0 for bending radius calculation.

Tekla Structures applies the unfolding ratio if the profile properties are within the range indicated by the minimum and maximum values.

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