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Stability Analysis According to
Eigenvalue Calculation Method
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Use RF-STABILITY to analyze the stability of structures. The RFEM add-on module determines critical load factors and the corresponding stability modes.
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| Features
- Calculation of structures consisting of member, shell and solid elements
- Import of axial forces of a load case or a load group
- Non-linear stability analysis
- Influence of axial forces from prestress can optionally be taken into account
- Equation solvers facilitating effective calculation of various structures
- Option to reduce stiffness by means of partial safety factor gM
- Visualization of stability mode
- Basis for calculation with imperfect equivalent structures in connection with RF-IMP
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| Input
First you select a load case or load group whose axial forces you want to use for the stability analysis.
To take into account a prestress, you can select another load case or load group additionally.
Then you decide if you want to perform a linear or a non-linear analysis.
Depending on the case of application, you select the subspace or the ICG iteration method.
Members that are not integrated in surfaces are normally represented as member elements with two FE nodes. With such elements it would not be possible to consider the local buckling of an individual member. Therefore, the module provides the option to divide such members automatically. |
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| Calculation
For the eigenvalue analysis two methods are available for selection:
- Subspace Iteration Method
The subspace iteration method is suitable for small- and medium-sized structures. It represents a fast matrix solver method requiring a large amount of random access memory (RAM) in the computer. For 64 bit systems a special solver version is installed. This solver can utilize significantly more memory. Therefore, it can also be used for a fast calculation of complex systems.
- ICG Iteration Method (Incomplete Conjugate Gradient)
This method requires only few memory. The eigenvalues are determined one after the other. This method should be used if you want to calculate big structural systems with few stability modes.
You can also use RF-STABILITY to perform a non-linear stability analysis. It provides results close to reality also for non-linear systems.
With this calculation method, the program determines the critical load factor by increasing step by step the loads of the underlying load case until instability is reached. During the increasing process, RF-STABILITY takes into account non-linearities such as failing members, supports and foundations, as well as material non-linearities. |
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| Results
The critical load factors are shown in the first results table making the evaluation of stability risks easier.
In case the structure contains members, the members' buckling lengths and critical buckling loads are also displayed in tables.
By means of the graphical output of eigenvalues you can evaluate the buckling behavior. The graphical display helps you to decide which countermeasures must be taken. |
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Note
You can find more information about RF-STABILITY here:
Download
Download the free demo version of RFEM and its add-on modules.
Request information
Get the detailed product brochure available for download. On request, we send you the brochure including a demo DVD directly by mail.
1.1 General Data
2.1 Critical Load Factors
2.2 Buckling Lengths and Critical Loads
2.3 Eigenvectors by Node
2.4 Eigenvectors by Member
2.5 Eigenvectors by Surface
