RFEM 5 - Buckling analysis with laminate material

[AtlasHalo]

Moin,

I am currently conducting buckling analyses with my models in the RF-Stability module. The latest version of RFEM 5.40.01 is being used.

My model is built as follows:

I have a steel structure, as shown in the image above. I am interested in the buckling behavior of the two red walls. Two different rectangular loads act from above. The gray material is wood, which was modeled using RF-Laminate. The structure beneath the wood looks as follows and consists of steel. This only serves for force transmission and does not actually exist in "real life."

The wood on my structure is meant to model 200mm thick wooden beams (these lie along the y-direction), on which, for example, a crane or excavator stands. The RF-Laminate consists of one layer with the following properties:

This approach leads to reasonable results for the strength consideration. Now I want to examine the buckling behavior. However, due to the RF-Laminate, my model only “buckles” within the wood plane (xy-plane)

Is a buckling analysis with RF-Laminate basically possible? What improvements exist for my special case?

[gerhard.rehm]

Hi AtlasHalo,

Thank you for your message!

To analyze the problem more precisely and to get a sense of the model's size, the model file would be very helpful:

Click on File → Save As and choose the following settings to reduce the file size:

Then upload the file here (e.g., *.rf6, *.rs9) – this way the community can also contribute to the solution.

Don’t want to share the file publicly? No problem – send it to me via direct message: click on my profile picture or my username → Message.

Best regards
Gerhard Rehm

[AtlasHalo]

Hello,

I would actually be reluctant to share the model, neither publicly nor privately. I would first need to clarify this internally and/or create a reduced model of it.

Regarding the shear stiffness, it is definitely due to the G_xy module. If I increase this significantly, no more "bulges" appear within the xy-plane, but rather where I would actually expect them. However, this is more of a workaround. Because in reality, there are simply wooden beams placed next to each other, which do not have shear stiffness relative to each other.

I would be interested to know if it is possible to exclude or ignore elements or surfaces from the bulge analysis.

[gerhard.rehm]

Hello, OK, but this way it will be difficult for us to find a possible input error. Excluding elements from the stability analysis of course does not work, since these elements influence the overall stiffness matrix. However, you can output eigenmodes only from a certain bifurcation load factor: