| Applies To | |||
| Product(s): | AutoPIPE | ||
| Version(s): | 2004, XM, V8i | ||
| Area: | Warning | ||
| Original Author: | Bentley Technical Support Group | ||
| Date Logged & Current Version | Feb. 2015 09.06.01.10 | ||
Problem:
The following occurs when running a modal analysis:
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Warning
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W801-14: No frequency below cutoff value
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OK
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Why does this occur and how to avoid it?
Solution:
Essentially the message indicated on the warning is correct, there are no frequency that can be calculated for the piping system model based on the modal analysis settings.
Avoidance:
On the Modal tab of the Dynamic Analysis dialog, enable the "Analyze up to Cutoff" option and increase the "Cut-off Frequency (Hz):" setting as needed. In addition, open Edit (Home > Model Options > Edit) dialog, set "Mass points per span" = A (Automatic), and update the "Cutoff frequency" setting as needed. Now analyze the system, if this warning message appears again, increase the "Cut-off Frequency (Hz):" to a higher value until such time the modal analysis runs without the warning appearing. This may be a repetitive approach.
Typically this message appears for models that have a unusually high 1st mode of vibration sometimes attributed to piping systems that are very stiff or have very little flexibility.
Another known issue is related to a corrupted model, review a complete Results output report with complete model input listed option enabled. Check the report for strange characters, bad settings, or NAN (Not a Number) value. Repair the model as needed and try to run a modal analysis.