×
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

post tension equivalent frame

post tension equivalent frame

post tension equivalent frame

(OP)
Would like to use generic stiffness analysis computer software to analize a post-tensioned beam - column frame for lateral loads. To include the post-tensioning as a load case for column and foundation design, are the secondary moments added as concentrated moments at the beam column joints or perhaps the unbalanced post-tension uniform load added to the beams?

RE: post tension equivalent frame

timothyg6,

The secondary prestress moments are the result of Secondary Prestress Reactions.

Use the reactions.

RE: post tension equivalent frame

Theoretically, you will need to apply secondary reactions to your lateral model. The secondary reactions, however, typically are very small and most times they are negligible. Sometimes we spot check the magnitude of the secondary reactions, but we never apply secondary reactions in the lateral model. Any more comments, Rapt?

RE: post tension equivalent frame

I have wondered this same exact thing. I haven't done PT in a while, but some other engineers I know that do it all the time also do not include secondary forces/moments in their lateral model. I questioned whether it should be included and was basically told it would not matter. I don't know about that one until I prove it for myself, I tend to not take someone's word when it comes to analysis.

RE: post tension equivalent frame

CoreyGuo,

Yes, they are normally pretty small compared to the applied vertical load effects but not always depending on the prestress arrangement. I think most people ignore them unless they are significant.  

RE: post tension equivalent frame

Rapt,

I've designed several different types of PT structures and I did pay some attention to the secondary reactions. I never see any significant seacondary reactions in comparsion with the reactions from graviy or lateral forces. I wondering when these secondary reactions could be significant. We ceryainly need to take the significant reactions into consideration. Do you realize any situations that require your attention?

Thanks!

RE: post tension equivalent frame

CoreyGuo,

It depends how close your tendon profile is to a concordant profile. For a concordant profile the secondary reactions are zero. The more removed the profiel is from concordant the larger the secondary reactions.

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