For a project in my studies, I am trying to model a steel-concrete composite bridge in RFEM 6. For this, I created the composite action via shared nodes using member eccentricity, as described in forum 001490 (members and connections also every 1.25 m).
When calculating the load due to self-weight (as a test calculation), I get the error message 10060 "The stiffness matrix is singular, the structure is unstable, FE mesh node no. X (number varies) in direction X."
Unfortunately, I do not know how to fix this error. The bridge actually consists of two composite girders. I first modeled one girder, which I want to copy and connect with the other once the calculation works.
Currently, you have not created any objects that can carry loads. At the moment, only lines are present. Normally, this is not a problem, but the line release leads to instability in the system. You need to create bars on the lines.
Additionally, the release is open in all degrees of freedom and without spring stiffness. It would be advisable to represent the composite conditions as realistically as possible here to stabilize the simulation.
If you need any support with modeling or settings, just let me know!
Hello Fabian, thank you for your response. I have no idea why the bars were deleted. I defined the bars with eccentricity top/bottom (I hope that is now visible in the model). Can you help me with the representation of the release? I don't know how to define it so that the conditions are realistic. Thanks in advance for your support! Verbundbrücke.rf6 (1.6 MB)
You can specify the corresponding stiffnesses in the line release type.
Which stiffnesses apply depends on the type of composite. I'm not an expert on that either and would refer you to literature; you will surely find something there.
If you continuously apply headed dowels, a rigid composite can be assumed as far as I know.
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