Hello,

i’m a student working for the first time on Grasshopper and Karamba and i need an help from you.

I’m trying to create a model of a steel frame shed in order to have from Karamba (using the CrossSectionOptimizer component) a pre-dimensioning of the whole structure and then export it to another fem program to check the result.

Starting from Jukka MÄENPÄÄ master thesis publied in Karamba website i’m wondering about the reliability of results specially in the case of critical design due to Lateral torsional Buckling or bending+compression.

Is there any strategy to make the results for these cases more reliable?

i’m comparing model made with same load cases and same buckling lenght

Hello @piovesan.marco93,

the steel design procedure in Karamba3D is according to EC3 (see here, and here).

When using characteristic loads limit the utilization to 70% (i.e. MaxUtil = 0.7). Set the buckling length of your members via the ModifyElement-component (see here).

– Clemens

Thanks Clemens for your reply,

I have another question: is it possible to show which verification is critical for any beam in the calculation of utilization rate?

I’m trying to understand how do Karamba perform calculation doing some comparisons with hand calculations and staad results.

For example i’m having trouble in explaining me the difference in shear utilization which i expect to be V_util=Ved/Vrd.

i add the attachment of the file i’m using for comparison and the image of an excel table with comparison between karamba and staad util rate.

Thanks for your patience (and sorry for my bad english)

Dear @piovesan.marco93,

I can not run your definition because I do not have the files referenced there.

Try the following: Isolate the beam which gives the weird results. This makes it easier to spot the problem.

The utilization is output for the point along a beam which gives the largest overall utilization. It could be that there the utilization due to shear forces is small as compared to e.g. the utilization due to bending moments.

– Clemens