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Dipl.-Ing. (FH) Robert Vogl
2020-01-29

Applying Imperfections in RF-/FE-LTB Based on Mode Shapes

I have defined a pre-deformation in RSTAB. When FE‑LTB imports the loads, why not also the imperfection?

Answer:

According to EN 1993‑1‑1 and DIN 18800 Part 2, equivalent geometric imperfections must be specified for calculations according to the second-order analysis in order to account for geometric and structural imperfections. This pre-deformation should be applied as affine to the lowest buckling or lateral-torsional buckling mode.

Therefore, in the FE‑LTB program, the eigenvalue belonging to the smallest mode shape is calculated (preliminary eigenvalue analysis) and then selected as the initial deformation mode. The imperfection approach is then carried out by the user scaling the mode shape.

Thus, the pre-deformation is based on the mode shape in RF‑/FE‑LTB. The imperfections defined in RFEM/RSTAB are irrelevant and are therefore not adopted.

Selecting Imperfection
Selecting Imperfection

Author

Mr. Vogl creates and maintains the technical documentation.

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