The following occurs when running a modal analysis:
---------------------------Warning--------------------------- W801-14: No frequency below cutoff value---------------------------OK ---------------------------
Why does this occur and how to avoid it?
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.
"Warnings" Messages
Bentley AutoPIPE