FAQ 004657 | I get the error "The stiffness matrix is singular!" for a calculation in RF‑FORM‑FINDING, what can I do?

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08/25/2020

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Thomas Günthel

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Question

I get the error "The stiffness matrix is singular!" for a calculation in RF‑FORM‑FINDING, what can I do?

Answer

In principle, the calculation with RF‑FORM‑FINDING has the same requirements as the calculation without this add-on module, so the criteria for general instabilities should be checked (see Links).

However, problems often occur with RF‑FORM‑FINDING because the form-finding process has been activated for too many elements. Therefore, you should check whether the correct (necessary) elements have been activated (see Figure 01).

In the following example in Figure 02, the form-finding has been activated for all horizontal members. This results in the error "The stiffness matrix is singular!" (see Figure 03). If you deactivate the beam members, the calculation is successful (see Figure 04).

Keywords

Dlubal FAQ Form-finding Unstable Singular Stiffness matrix Frequently Asked Question FAQ about Dlubal Question and Answer about Dlubal

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  • Updated 11/09/2020

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