×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

need instructions for vibration (modal) analysis

need instructions for vibration (modal) analysis

need instructions for vibration (modal) analysis

(OP)
I have a simple 3D truss that will be used to support a small wind generator.  My truss is subjected to a gravity joint dead load and a joint wind load due to the wind generator.  I feel fairly confident that I am capable of performing a vibration analysis of my truss (the wind generator company wants to ensure the natural frequency of my truss does not match the natural frequency of their wind generator).  I would appreciate it if someone could provide step by step directions detailing how to perform a vibration analysis and review the output.  Thank you.   

RE: need instructions for vibration (modal) analysis

Dear skicat,
            first of all make your model, with the proper stiffness and masses. If you want to consider same load as a mass for the dynamic analysis, go to define/mass source.

When you run the analysis, activate "MODAL CASE" (as default is activated).

Then you should go to display/show deformed shape/ pick the modal case and the mode number. On the display you can see the period of the structure.

Bets regards,

Sebastian

RE: need instructions for vibration (modal) analysis

Exact like Sebastian mentioned

But you mentioned a 3D truss, and that makes correct modelling tricky. It all depends on how your mass is distributed on your truss and the presence of very weak elements.

Please check the modeshape to see that the first one you get moves the whole truss together, not just a few parts. The period you get for this modeshape will be the correct one.

If your first modeshape shows only a few elements moving while others are almost stationary, that will be a bad mode and wont really represent your frequency

Distribute your mass carefully, realistically.

respects
ijr

 

RE: need instructions for vibration (modal) analysis

(OP)
Thank you both very much for your help.   

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources