Structure Stability for RFEM 6

• Calculation of models consisting of member, shell, and solid elements
• Nonlinear stability analysis
• Optional consideration of axial forces from initial prestress
• Four equation solvers for an efficient calculation of various structural models
• Optional consideration of stiffness modifications in RFEM/RSTAB
• Determination of a stability mode greater than the user-defined load increment factor (Shift method)
• Optional determination of the mode shapes of unstable models (to identify the cause of instability)
• Visualization of the stability mode
• Basis for determining imperfection

You can select several methods that are available for the eigenvalue analysis:

• Direct Methods
  • The direct methods (Lanczos [RFEM], roots of characteristic polynomial [RFEM], subspace iteration method [RFEM/RSTAB], and shifted inverse iteration [RSTAB]) are suitable for small to medium-sized models. You should only use these fast solver methods if your computer has a larger amount of memory (RAM).
• ICG Iteration Method (Incomplete Conjugate Gradient [RFEM])
  • In contrast, this method only requires a small amount of memory. Eigenvalues are determined one after the other. It can be used to calculate large structural systems with few eigenvalues.

Use the Structure Stability add-on to perform a nonlinear stability analysis using the incremental method. This analysis delivers close-to-reality results also for nonlinear structures. The critical load factor is determined by gradually increasing the loads of the underlying load case until the instability is reached. The load increment takes into account nonlinearities such as failing members, supports and foundations, and material nonlinearities. After increasing the load, you can optionally perform a linear stability analysis on the last stable state in order to determine the stability mode.