The tabs that allow you to assign support points and support lines are very similar. That is why we will examine them together.
Top part
- With the quick buttons on the left you can allocate typical points or line supports.
Depending on the chosen quick button, the relevant degrees of freedom will be set fixed in the middle part of the dialogue (see next paragraph).
- The right shows a graphic representation of the restricted degree of freedom
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The orientation of the representation changes with the orientation of the global coordinate system
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If you selected several points before opening the dialogue, the point with the lowest point number is displayed in the representation.
Middle part
Here you can restrict the various degrees of freedom directly. For each degree of freedom, using the pull-down menu, you can:
- set the degree of freedom fixed.
This can also be done by checking the check box before the degree of freedom. - enter a translational or rotational spring (depending on whether the degree of freedom is a displacement or a rotation) using a value.
Examples on how to calculate a translational spring, can be found here. - enter a function (more info).
You can also indicate for each translational spring that it cannot absorb any negative (tensile) or positive (compression) reaction. For example, in the global Y-direction, this means that an upwards or downwards displacement of the structure is not hindered.
Bottom part
By rotating a support, you impose a relation between the restricted degrees of freedom. As a result, the rotated support might not work as you expect it to work. An worked example with how rotated supports really work can be found here.
Here you set the orientation of the support point using the angles α and β:
- α will rotate the support point in the YX plane.
A positive angle is equivalent with a counter-clockwise rotation. - β will rotate the support in the XZ plane.
A positive angle is equivalent with a clockwise rotation.
To give a rotation to a line support:
- check the option ‘Restraint defined relative to line orientation’.
- Enter the angle α through which the supporting point must be rotated.
Lines are characterised by a local coordinate system. Support lines can thus be rotated in a simple way according to the local coordinate system of the bar.
