Results mismatch in Steel member design Karamba & Robot

I have created a portal frame in GH & designing in Karamba and comparing results of Utilization of Elements in Karamba vs Autodesk Robot. The results seem to be similar for beams, but for columns they don’t match. Refer screenshots. Please help me on this. I am also confused how to read Karamba UR details. Refer screenshots please.




Portal frame with Karamba_With space optimisation_with purlins.gh (65.3 KB)

It is difficult to see the differences in the results when there are only some screenshots and the Karamba3D model.

One way is to use the values from the Details output and compare those to those of your Robot calculation to see if Robot gives you the same values. Also, check if the buckling lengths have been defined properly in both as this can also affect the results in Karamba3D.

Hi @matttam Thankyou for responding to me. Please find screenshot of design results of same column element (element number 42 in RSA and element no 01 in Karamba). I did check analysis results (like Mx,My, Mz, Vx, Vy, Vz) are mostly matching between Robot & Karamba. However the UR ratios specifically for column are not matching. I checked buckling length, and they are matching.

Can you please explain me why the UR ratios aren’t matching in softwares.

Also Can you explain me what all these terms in karamba design detail output mean. Refer screenshot below.

Screenshot of Robot output below (for same column)

Please explain which values to directly compare between Robot & Karamba please.

Hi @Neeraj_Khatri,
it is hard to tell what might be the reason for the different results from just looking at the print outs. Could you provide a small example with e.g. one column where the comparision fails?

Maybe you find this post helpful: Results differ from Karamba and FEM-design - Grasshopper / Karamba3D - McNeel Forum. In one of my responses you will find the C++ sourcecode attached which is used to calculate the utilization based on EC3. It is not very complicated to read and contains references to the design formulas in EC3.

The ‘SwayFrame’ option can have a large impact on the results.

– Clemens

Can you help me with what the values in Karamba Design output mean. Refer screenshot below.

The values listed are intermediate results of the design procedure according to EN 1993-1-1 (see here and here).
– Clemens