Find Mode Shapes From Critical Load Factor
Tips & Tricks
The function, which is also known as shifting, allows you to calculate critical load factors beyond a user‑defined initial value. A determination of the critical load factors is usually done from the smallest to the greatest critical load factor.
If you define a value for shift f0, the characteristic polynomial is shifted by this value to the origin This has the effect that the calculation first converges to the next greater critical load factor beyond f0. When using this function, please note that critical load factors smaller than f0 cannot be determined.
If, for example, a model has the critical load factors (eigenvalues) 2, 3, 4, 5, 7, 8, 9, 11, 15..., and if you select a shift of f0 = 7, then the critical load factors 8, 9, 11, 15... are determined.
Dipl.-Ing. (FH) Adrian Langhammer
Product Engineering & Customer Support
Mr. Langhammer is responsible for the development of the add-on modules for reinforced cocrete, and provides technical support for our customers.
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The calculation can be terminated due to an unstable structural system for various reasons. On the one hand this can indicate a ‘real’ instability due to an overloading of the system, on the other hand the error message can result from inaccuracies in the model.
The number of degrees of freedom in a node is no longer a global calculation parameter in RFEM (6 degrees of freedom for each mesh node in 3D models, 7 degrees of freedom for the warping torsion analysis). Thus, each node is generally considered with a different number of degrees of freedom, which leads to a variable number of equations in the calculation.
This modification speeds up the calculation, especially for models where a significant reduction of the system could be achieved (e.g. trusses and membrane structures).
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Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements
Stability analysis according to the eigenvalue method