If numerical instability occur within an ETABS model, we recommend considering the basic troubleshooting techniques which follow:

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• Releases. Do not release moment for objects adjoined at the same joint, such as with beam-column connections. Also, do not release moments at the base of a column that has  a pinned restraint (i.e moments rotations allowed).  Multiple coincident releases will cause numerical problems. If necessary, one object may be released.

• Self weight. Ensure that deflected configuration under self-weight is as expected.

What does it mean when numerical instability warnings are reported, but there is no joint at the location indicated?

Answer: Numerical instability is reported according to numerical formulation and the sequence in which equations are solved. The point indicated is not necessarily a discrete point at which instability occurs, but rather a location related to the assemblage of objects with significantly different stiffness.

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Refer to page below  for further recommendations:

See Also

• Lost digit of accuracy and Ill-Conditions

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