Member Login

Remember Me
Forgot Password?
Join Us!

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!

Join Eng-Tips
*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.

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

Vertical distribution for base shear determined by response spectrum

Vertical distribution for base shear determined by response spectrum

Hey. I’m doing a response spectrum analysis as per section 12.9 of ASCE7-05. It does not address how to distribute the seismic base shear (like the equivalent lateral force procedure does). As I recall, there is some formula to use (i.e. F(level)=participation factor x mode shape vector x acceleration x etc.,etc.). Does anyone have an opinion on this? Does STAAD perform this for you?

RE: Vertical distribution for base shear determined by response spectrum

The formulation u have mentioned is correct. Seismic base shear in RS is done based on the mass participation factor. So according to the time priod of the structure in different modes it (STAAD) reads corresponding acceleration from the graph you have entered into it and then simply gives u the base shear as = acc.*mass part(%)*weight for the particular mode. For all the modes listed it sums up based on the ABS/CQC/SRSS methods and then gives u the total base shear.
Be aware that STAAD gives all the forces (support reactions, member forces, etc etc) ignoring their sign...meas for a horizontal seismic force on a portal frame it gives both the support reactions +ve (insted of one +ve & other -ve).

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!


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