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Answer: Numerical instability warnings indicate that digits of accuracy were lost during computation.
Software performs computation with 16 digits of accuracy, some of which may be lost when analysis involves systems of significantly different stiffness, in which lower-order values are truncated to suit operations with higher-order values. When this warning occurs, ETABS reports the location of the occurrence such that the user may edit the model if necessary.
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- Over 11 digits lost causes analysis to terminate because an Ill-condition warning at the end of the analysis and results may not be sufficiently accurate. ETABS indicates the location of the numerical problem, and presents a warning message which prompts in this case the user needs to check and revise the model.