Hello, I am trying to undertake a buckling analysis of a truss bridge in Karamba. I am struggling to understand the buckling analysis in Karamba and the correct ordering to place the components. I am based in the UK so design according to Eurocodes.

BS EN 1993-1-1 cl 5.2.1 only requires 2nd order effects to be considered if the elastic critical buckling factor is greater than 10. However, Karamba seems to require the ThII component before the buckling analysis component. Therefore, I am not clear if the results of the buckling analysis are the elastic critical buckling factor as they already include 2nd order effects. Can anyone clarify?

cl 5.3 requires consideration of initial imperfections (Geometric nonlinearities) when undertaking a second-order analysis. I would normally use the eigenvector deformed shape, normalised to the geometric imperfections but I can’t see a way to connect the external loads to the deformed model to input into the non-linear analysis.

Finally, I only want to undertake a geometric non-linear analysis - ignoring material non-linearities. Is there a way to control this with the non-linear analysis component?

hopefully the above is clear, any help would be greatly appreciated.