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

Converting 5% damped response spectrum to 2% damping

Converting 5% damped response spectrum to 2% damping

Converting 5% damped response spectrum to 2% damping

The USGS spectral response graphs are all based off of 5% damping, however IEEE-693 (6.9) and ASCE 113 ( for electrical substation design both state that a maximum damping value of 2% must be assumed for all structures.

These structures are basically inverted pendulums supporting relatively massive equipment and so 5% damping is very unlikely.

Is there a good way to convert the USGS 5% damped response spectrum into a 2% damped one?

I have found Figure 2-1 of Fema273 which shows how to build a generalized response spectrum.

These factors are the same as ASCE 7-10 (and ASCE 7-05) table 18.6-1

But this paper here indicates that there is a very large scatter to the data which produced these damping modification factors:

Does anyone have any comments? Why doesn't the USGS tool allow you to specify the damping ratio? It seems like they would have the capability if they already have all of the earthquake data to create 5% spectra.

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


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