Finding System Instabilities
Tips & Tricks
A calculation break‑off due to an instable system can have different 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.
To find modeling errors in the structural system, RFEM offers you several elegant options to localize and analyze them. To this end, a new feature was implemented in the RF‑STABILITY module, too. The option “Calculate buckling shape for unstable model so that causes of instability can be checked graphically” allows you to calculate supposedly instable structural systems. With the model data, the module performs an eigenvalue analysis so that the result of the instability of the affected structural component is shown graphically. This method is particularly suited to find, for example, members that are not connected or that have too many open degrees of freedom.
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Models to Download
Knowledge Base Articles
If a member is laterally supported due to a compressive axial force to prevent buckling, it must be ensured that the lateral support is actually able to prevent buckling.
Frequently Asked Questions (FAQ)
- How does RF‑STABILITY or RSBUCK determine the buckling load? According to the manual calculation, the respective buckling loads should be about 10% higher.
- Why is it not possible to use result combinations in RF‑STABILITY? It is possible in RSBUCK indeed.
- How can I design any SHAPE‑THIN cross-section in detail in RFEM or RSTAB?
- I have calculated a pre-deformed structure according to the second-order analysis with RF-STABILITY and RF-IMP. Why are the deformations of the CO smaller than the applied pre-deformation?
- Is it possible to perform stability analyses on reinforced concrete structures by means of RF‑STABILITY?
- How can I perform a buckling analysis for a surface in RFEM?
- Is it possible to import effective lengths from RF‑STABILITY or RSBUCK in RF‑/TIMBER Pro?
- What is the critical load factor and how is it possible to determine it?
- What is the purpose of the "Calculate eigenvector for unstable model..." option in RF‑STABILITY?
- Why are the stiffness modifications not taken into account when determining critical load factors in the RF‑STABILITY add-on module?