Using the “Buckling Mode” imperfection type and the “Automatic” source type, you can have RFEM and RSTAB automatically determine geometric equivalent imperfections. This is based on the mode shapes calculated using the Structure Stability add-on. The initial bow can be specified as a relative value or in accordance with EN 1993-1-1.
RFEM/RSTAB determine the load combinations in two consecutive steps: First, the structural analysis and linear stability are determined, and based on these, the magnitude of the imperfection is calculated for each governing stability mode. Next, the combination with the derived geometric equivalent imperfections in both the positive and negative directions is calculated for each stability mode.
This allows you to obtain results that comply with standards based directly on the actual bending and buckling shapes of the model, without having to determine the imperfection values yourself.