×
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

Moment Frame - Rigid & Pinned connection

Moment Frame - Rigid & Pinned connection

Moment Frame - Rigid & Pinned connection

(OP)
I am designing a special steel moment frame building with 2 bays in one direction.  Due to the wide flange column configuration I cannot do a moment frame with fixed ends at each column.  Looking at a bay I have two beams connecting with a pinned connection to the outer columns and connecting rigidly (moment) to the center column, thus two half frames.  I am designing this under the 06' IBC and the AISC 341-05 seismic provisions for SMF (special moment frame) conditions.

Does anyone know if there is a code violation of not using a frame fixed at both ends?
Thanks in advance.

RE: Moment Frame - Rigid & Pinned connection

I have seen this done in other countries (non-seismic) where a big column is used in the center and small pinned ones on the outside walls. It seemed to work fine.

Under lateral load it works kind of like outriggers in a high rise, one external column goes into tension and the other into compression.

I wouldnt use 2 half frames though it is virtually a mechanism.

csd

RE: Moment Frame - Rigid & Pinned connection

If you are using an SMRF, what you are doing is not acceptable. All the AISC pre approved connections assume plastic hinges to form at certain location at both ends of the beam.

RE: Moment Frame - Rigid & Pinned connection

I think that you should model this frame with some software like ram advance or risa 3d.  For this kind of structure  the R factor should be very low Lets say 2.2 or 2(like a cantilever column). You should be conservative and show the plan checker that this structure really works. The main problem would be the ductility of the structure that is unknown because you don´t have any test that could prove the really ductility of the sistem.

LG

RE: Moment Frame - Rigid & Pinned connection

(OP)
I modeled the building in ETABS, and it appears to work fine.  Drift significantly controls the design of the frames.  I couldn't find anywhere in the seismic provisions (AISC 341) nor in FEMA 350 where you had to have two plastic hinges, one at each end of the beam.  They address the connection and the beam and column relationship.  The connection satisfies SMRF requirements.  Are you aware of anywhere in the codes that specifically suggests that this is not allowed?

RC

RE: Moment Frame - Rigid & Pinned connection

Doesnt it have two hinges - one on each side of the middle column?

RE: Moment Frame - Rigid & Pinned connection

(OP)
Yes it has two hinges, one on each side of the middle column.  However each beam only has one hinge.

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