Hybrid cross-section with different values depending on the load

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X-plane.V2.rf6 (1.9 MB)
Can I model a member that has a different cross-section depending on if it is in tension or compression?

I have this 2D model of a timber facade, with the majority of the members made out of glulam. However, there are a couple of diagonal members with two steel plates running all the way through. To model this I have made cross-sections in rsection-1. The problem I have is that for the members with the custom cross-sections is that the timber and steel work together in both tension and compression. I want this for the members in compression, but for the members in tension only the steel should work/resist. This is due to the design of the building. Right now I have changed the cross-section of the members in tension to a steel cross-section, but this would mean that I can't change the load case without changing the cross-section. Ideally I could model it in a way that the timber is neglected if a member is in tension, but is this possible or is there a different solution?

Thanks for your help!
Kind regards,
Daan
t10.rsc (754.3 KB)
t20.rsc (756.4 KB)

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Hi D.Eggenkamp,

That’s an interesting question! :smiley:

Currently, RFEM 6 does not offer a direct way to define different cross-sections based on the type of axial force. However, whether a solution is possible depends a bit on the specific focus of your analysis.

Possible Approaches:

  • Realistic internal forces in the 3D model: If your goal is to determine realistic internal forces within the 3D model and account for the nonlinear structural behavior of the member, it might be possible to use a more realistic modeling approach for the composite member. This could involve a volume model with nonlinear surface contact between steel and timber.

  • Cross-section design with "Timber Design" and "Steel Design" Add-Ons: If you intend to design the cross-section using the Timber Design and Steel Design Add-Ons and perform the corresponding design checks, one approach would be to define a result member that uses only the cross-section of the steel profile but still applies the internal forces from the composite beam.

If you need more details or guidance on this, feel free to let me know! I’d be happy to help further. :blush:

Best regards
Niklas Wanke

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