Line Release in Model with Several Surfaces

Tips & Tricks

The following post describes two different types of line release definitions.

As an example, there is a simplified model consisting of a member grid (red) and four surfaces (type: membrane, defined as strips). The membrane should rest on all members in the case of wind pressure or should be held by the outer frame in the case of wind suction. This is possible by defining a nonlinear line release type. In the subsequent definition of the objects to be released, two different cases may occur.

  • Case 1 (in the middle): Only the surface is released, which includes the selected line.
  • Case 2 (on the right): The surface is released, which includes the line and the adjacent surfaces. (*Note)

The deformation graphics clearly show the difference. If you release the single surface (Case 1), the contact between the surface and the line is detached but the nodes connect the surface with the member as before. The behavior of the deformation graphic on the right (Case 2) complies with the requirements. The surface is detached from the central member completely.

*Note:
There is a certain semi-automatism in the surface selection. For each line, it is possible to release only one new surface. This can be explained in detail on the right model: For each line (four pieces), one line release has to be defined. In theory, the first line release on Surface 9 requires the release of Surface 9 and 10. However, only Surface 9 is accepted. Now, the second line release is defined on Surface 10. In theory, Surface 9, 10 and 11 have to be released.

However, only Surface 9 and 10 are accepted. At this point, the semi-automatism takes effect. Now, if you edit the first line release again, you can see that Surface 10 is added automatically. Therefore, the definition is correct. If you create the third line release, only Surface 10 and 11 can be released. After the definition, the program adds the previously missing Surface 11 to the second line release automatically.

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RFEM Main Program
RFEM 5.xx

Main Program

Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements