Error 10134 | The stiffness matrix is singular

[Tk259]

I have recreated the steel framework from the webinar "Modeling and Design of Steel Structures in RFEM 6 | Part 1: Modeling, Load Input" and believe that I have not introduced any errors.

During the calculation, I receive the error at nodes 2 & 10 for various load cases: "The stiffness matrix is singular | The structure is unstable | FE mesh node no. 2, in X direction, increment 1."

Notably, the error only occurs in load combinations (2, 8, 14, 40, 46) where the imperfection in the Y direction is considered and not the one in X. After some research, I found out that the tension members need a kind of "activation" to work properly. The imperfections apparently handle this. However, this does not work when the imperfections in the Y direction are used. The load combinations were created with the assistant as shown in the webinar.

Why does this error occur for me, although it does not occur in the webinar?
1_Stahlgerüst.rf6 (1.5 MB)

[stefan.hoffmann]

Hi Tk259,

Welcome to the community! Glad to have you here.

In this FAQ you will find various approaches to analyze the cause in more detail:
https://www.dlubal.com/de/support-und-schulungen/support/faq/005345

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What is the cause in your case?

In your model, the tension members fail simultaneously. As a result, they lose their effect in the system.

Quick solution

A simple and proven measure is to apply a small prestress to the tension members.
This ensures that the members remain active and are not deactivated simultaneously.

Best regards
Stefan Hoffmann