[DE] FAQ 000468 | [*S14139565*] [*S14139566*] Therefore, dynamic calculation is not possible" or ...

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First Steps with RFEM

First steps

We provide hints and tips to help you get started with the basic program RFEM.

12/19/2019

001111

Robert Vogl

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Question

When performing a dynamic calculation, I get the message: "The model has no free mass assigned. Therefore, dynamic calculation is not possible" or "Too many eigenvalue required." How can I calculate mode shapes?

Answer

It can be determined as many eigenvalues as there are degrees of freedom in the structure to which a mass is assigned. In order to determine the number of degrees of freedom, the number of nodal points of FE nodes must be multiplied by the active mass directions. The masses in fixed supports are not considered for this as they cannot freely oscillate.

If the 'Division for Straight Members' (RFEM)/'Internal Member Division' (RSTAB) is not activated, B for single-span beams, masses only exist in the supports and thus no eigenvalues can be determined. In such cases, activate the member division as shown in the figures.

Since the Lanczos solver in RF-DYNAM Pro cannot determine all existing eigenvalues, the "root of the characteristic polynomial" solving method can also provide remedy.

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Dlubal FAQ Frequently Asked Question FAQ about Dlubal Question and Answer about Dlubal

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  • Updated 04/09/2020

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