Modal Analysis, Modal force, Modal moment

Hello,

There are any approaches to see the "Force and moment at any points of model" in "Modal analysis". No time history or response spectrum. I just would like to see the force and moment when the model vibrates.

From my findings, I have seen that the eigen values files are contain the modeshape, force, and moment. However, there are no information about the unit of force and moment.

In addition, Does Autopipe export the modal stress at this moment?

Please kindly clarify and suggest me the approach.

Thanks

  • Greetings OTTAP, 

    Let us back up a moment.

    AutoPIPE produces the following reports:

    Results > Reports:

    • Accelerations

      Creates a section which lists the accelerations at each piping point calculated by the active dynamic analyses (Response spectra, Force spectra, Time History, and Harmonic).

    • Frequency

      Creates a section which lists the currently active range of natural frequencies calculated for the system by a modal analysis.

    • Mode shapes

      Creates a section which lists the translation (mass normalized), and rotation point displacements for each active mode shape. Unitless values because The modal displacements are mass normalized which means they divided by a matrix transformation.

    Furthermore, under Print> Report> are the following reports:

    • Modal Output

      Enable this option to print the modal output report associated with the current model. This option is only enabled once the MOD file has been created during dynamic analysis of time history and/or response spectrum. This option enables a user to print modal contributions in time history analysis to the MOD file each time the time history is analyzed. This includes, Displacement, Forces, and moments per mode shape. 

    A mode shape is only the response of the system due to an excitation. At this time there is no Forces and moment results generated purely for a Mode shape. However as mentioned above, the Modal ouput report generates Forces and Moment results.  

    Next, I have already answered your questions related to units of forces and moment at any point in forum posting here. I had also mentioned best to use the MOD file, which can be opened in any text editor. This file has column heading with units:

    Finally, about modal stress, No Stress are a post processor event that are calculated based on code equations using values from Displacement, Forces, and Moments from a given Load case, Ex Gr+MaxP, Sus+E1, Sus+M1, etc..

    Regards,
    Mike Dattilio
    Design Analysis Engineering Group
    Senior Analyst Bentley Systems Inc
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