Warning GFREQ=100Hz too long (factor4)

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ROHR2stoss - Structural Analysis with Dynamic Loads using Direct Integration
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r2user
Beiträge: 135
Registriert: Mi 14. Sep 2011, 10:18

Warning GFREQ=100Hz too long (factor4)

Beitrag von r2user » Mi 20. Mär 2013, 12:23

Dear ROHR2 Team,

As part of a pipe stress analysis, the load case earthquake should be considered. For this reason the load case eigenvalue was included with a cut-off frequency of 100Hz.
This calculation showed the following warning:
“line section 10- 20 at GFREQ= 100. Hz too long (factor 4)”

What is the meaning of this warning?

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rohr2support
Beiträge: 393
Registriert: Mi 14. Sep 2011, 08:23

Re: Warning GFREQ=100Hz too long (factor4)

Beitrag von rohr2support » Mi 20. Mär 2013, 12:26

Hello User,
ROHR2 displays the warning “line section 10- 20 at GFREQ= 100. Hz too long (factor 4)” because of the fact that the calculation kernel has to insert several nodes at a segment. This is necessary in order to calculate the system up to a cut-off frequency of 100Hz.
This nodes are required so that the results can be determined with sufficient accuracy up to a cut-off frequency of 100Hz. This warning is not critical but necessary because the graphical interface knows only the user defined nodes. In this case the user defined nodes are not enough in order to display the correct results up to a cut-off frequency of 100Hz.

The following pictures display the problem. (Click to enlage)
Bild_GFREQ_1.png
Picture1 : The first eigenvalue is shown for two equal tubes with a different discretization in the graphical interface.
Eigenvalues and displayed deformation are equal.
Bild_GFREQ_2.png
Picture2 : The seventh eigenvalue is shown for two equal tubes with a different discretization. Warning is displayed because of the fact that the shown graphical result is not correct.
Eigenvalues are equal and the forces, moments and stresses at the nodes defined in the graphical user interface are equal as well!
So you can ignore the warning if you are sure that you don't have any relevant results at intermediate locations on your pipe.
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