Load removal of an area in RFEM5

Product Support
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1

Good day,
I have a question regarding the modeling of a surface.

I want the surface in the model to transfer its forces only to the crossbars, and the crossbars then transfer the load into the two main beams. The bars in the model each have a predefined cross-section. Can you help me with the modeling?

Thank you very much for your help!

3

Hello,

Such behavior can be achieved in different ways.

The easiest way to decouple bars or lines is to use line releases. However, since these have to be defined separately for each line, I would personally recommend decoupling through modeling.

There are basically two options for this:

  • The surface can be modeled with a minimal distance to the edge bars. This decouples the elements from each other.
  • Alternatively, the bars, which are currently modeled using eccentricities, can be modeled with a real distance and then connected to the structure at the desired points using rigid bars.

Bars inside surfaces can also be decoupled by editing the integrated lines.

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Best regards
Eike Hartmann

4

Hello Mr. Hartmann,

Thank you very much for your help in advance.

How can I model the surface with a minimal distance to the bars? Don't I need the bars as boundary lines of the surface? And if the bars are the boundary lines, then they are automatically integrated into the surface, aren't they?

I have now modeled the bars with eccentricity as rigid bars, just as you suggested.

Best regards

5

Hello,
if you have already modeled the bars eccentrically, separate modeling is probably no longer necessary. The integration of lines within the area can also be manually deactivated, as described above.

Surfaces are bounded by lines. Lines are also the basis of bars. If a surface and a bar share these parts, they are automatically connected. A small distance between the edge line of the surface and the bar would represent a local decoupling (due to an offset modeling or the "Move and Copy" command). Thus, the surface and the bar no longer share a line.
Afterwards, you can manually connect the bars using rigid bars or couplings. An alternative to this would be line release.

Best regards
Eike Hartmann

7

Hello,
it seems to me that the model now contains objects that are connected to each other not via a beam or a surface, but via simple lines. These have no stiffness and therefore cause the singularity.

One method to investigate the instability is to perform the stability analysis with the settings shown in Image 1. This will provide you with a deformation pattern that can give clues about the location.

Kind regards
Eike Hartmann

Image 1:

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