×
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

Fundamental natural Frequency; Sign Poles

Fundamental natural Frequency; Sign Poles

Fundamental natural Frequency; Sign Poles

(OP)
How do you calculate the fundamental natural frequency and damping ratio for a sign structure?

RE: Fundamental natural Frequency; Sign Poles

This site (Florida DOT) has a list of downloadable programs (mathcad sheets, etc) for the design of many highway structures.  

http://www11.myflorida.com/structures/proglib.htm

If you don't have mathcad you might be able to load these in MathCad Explorer, downloadable from the www.mathsoft.com

The natural frequency is a function of the mass of the sign and structure, the Young's Modulus and Moment of Interia.

RE: Fundamental natural Frequency; Sign Poles

The fundamental frequency of an structural assembly properly modeled should be ascertainable from 3D programs with dynamics capability. Maybe even modest cost RISA 3D can do it even with hinge inserts. Respect damping ratio, Chopra gives
Under 0.5 Fy stress...
0.02 to 0.03 for nude steel welded structures
0.05 to 0.07 for nude steel bolted structures
Just prior to yiel Under 0.5 Fy stress...
0.05 to 0.07 for nude steel welded structures
0.10 to 0.15 for nude steel bolted structures
It is simpler to design in accord to a code, that in Spain exist, albeit it won't be suited for some high seismic places.
Respect attached weights (panels) the model should be as complete as to not need further separate (and worse) account.
Also is of relevance how account is made of Vortex Shedding, and of local over-pressures. Basically, either you design by a code, or you descend to the "truth" in the science of construction, what no doubt for cases will discover weaknesses of the approved codes for a thing like the one you attempt detailed analysis of.

RE: Fundamental natural Frequency; Sign Poles

Actually a sign would be pretty basic: it's just a cantilever (correct me if I'm wrong, and your sign is very complex). So the stiffness would be 3EI/L, and the cyclical frequency omega would be = sqrt(k/m).

RE: Fundamental natural Frequency; Sign Poles

I agree with abhio.  Programs may be required for complex calculations, but for a sign, its just a cantilever.  Make sure you're looking at the correct natural frequency. Omega_n is the angular natural frequency (rad/s) and the natural frequency f_n would be [Omega_n/(2pi)] (Hz).  

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