×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Structural Harmonics

Structural Harmonics

Structural Harmonics

(OP)
Does anyone know if there is a feature within RISA that would allow you to load a structure with sustained wind forces that would induce various modes of torsional harmonics through vortex shedding.

I have a pole structure with a large "sail" if you over about 2/3 of the length that has to be restricted in movement for the asssembly to serve its purpose.  I am worried about harmonically induced torsional deflections and am considering going to two poles instead of one to eliminate this problem.  The client may not buy the idea, but that's another discussion for another day.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Structural Harmonics

Vortex shedding....  I've always wanted to research this portion of the code more.  Ever since I took an aerospace structures course in college, I've been interested in the interaction of the aerodynamic and dynamic properties of structures. You don't often look at "Flutter" of airplane wings in civil structures.  Vortex shedding is as close as you get.  

RISA does not currently have the ability to do a harmonic loading or time history analysis.  The closest that we can get is by running a response spectra analysis / eigen solution.  The good news is that running an eigensolution / response spectra (while geared more towards earthquakes) will give you a ton of useful information about the dynamic properties and natural frequencies of your structure.  You can use that to determine if you are indeed in the range of frequencies where vortex shedding will be a potential problem.  

On another note, I always thought there were some simple modifications that you could make to a pole to reduce it's susceptibility to vortext shedding.  Akin to adding fins to the structure.  I'm no expert and am certainly over simplifying.  But, I do think I've read about known ways to effectively control that behavior.  

  

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! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close