×
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

Concrete Moment Frame - Strong Column Weak Beam at Interior column

Concrete Moment Frame - Strong Column Weak Beam at Interior column

Concrete Moment Frame - Strong Column Weak Beam at Interior column

(OP)
I couldnt find an (e) post for this so here it goes...

Problem: I have a single storey building with concrete moment frames.  I am aware of the Mnc>(6/5)Mnb criteria that that ACI 21.4.2.2 uses to ensure beam yielding prior to column yielding. For interior columns (where i have two beams frame into i column)I would require a very large column section to satisfy the above equation.

Question: Is there a provision where I would not require such a large column flex capacity in the ACI somewhere or even in the IBC 2006 ? Or even in the 2007 California Building Code?

Your help would be much appreciated!

RE: Concrete Moment Frame - Strong Column Weak Beam at Interior column

Consider 21.4.2.3 - if you can't meet Equation 21-1 in21.4.2.2, you can add additional transverse reinforcing.

Also, the commentary suggests (in ACI 319-02 - 4th paragraph of the 21.4.2 commentary) that if you don't meet the weak column criteria at a joint, then "any positive contribution of the column or columns involved to the lateral strength and stiffness of the structure is to be ingnored..."

...but you can't ignore "negative" contributions such that the siesmic demand is reduced because you ignore the stiffness contribution of these columns.

RE: Concrete Moment Frame - Strong Column Weak Beam at Interior column

It's not just a commentary suggestion.  21.4.2.1 mandates that any column that doesn't satisfy the SCWB criteria cannot be used as part of the lateral system.

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