×
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

Coninuous steel beams over columns

Coninuous steel beams over columns

Coninuous steel beams over columns

(OP)
I have a situation where my beam runs continuous over my column and cantilevers about 2' to pick up a small load. I usually try to avoid this detail but this time I cannot.

I have placed stiffener plates on each side of the beam, to help potential rolling over of the beam under earthquake load. I am considering the top of my column adequately braced in this situation. It seems that all this will work if the roof is adequately braced against moving (with small enough deflection).

I understand this detail is pretty common, but I am looking for any add'l opinions and this detail's success under seismic loading.

RE: Coninuous steel beams over columns

Do you have any members running perpendicular to this beam near the column.  Sometimes simply extending a bottom chord/flange angle to further prevent rotation might be a prudent detail in a seismic zone.  

That said, we just completed a warehouse project in Los Angeles where we had continuous beams over columns everywhere; used stiffener plates at all columns and did not use these extra angle braces.  

RE: Coninuous steel beams over columns

One add'l opinion. If torsion due to unequal rolling is feared, the stiffeners will not be resisting. In that case you have to check the beam for the torsional effects as well.

RE: Coninuous steel beams over columns

(OP)
Thanks guys!

RE: Coninuous steel beams over columns

I generally try to use continuous steel beams where possible and, except for very light loadings, always use stiffener plates.  The stiffener plates, in conjunction with 4 high strength bolts, normally provide sufficient resistance against 'tipping'.  I'm not sure why the reluctance to use beams over columns; it's a simple connection to design and analyze.

In addition, with continuous spans, the stiffeners provide additional assurance that the cross section will remain stable at the initial plastic hinge locations (even if not required, although there's not much redistribution with a cantilever <G>).  The continuity generally makes for more economical construction (smaller members and fewer pieces to handle).  It also provides an increased stiffness for deflection considerations.

I also almost never check for web crippling at supports, preferring stiffener plates; I use stiffeners almost all the time (except for very light loadings).

RE: Coninuous steel beams over columns

I would second dik's comments.  Our policy is to always use stiffeners when beams run continuous over columns.  flame's comment above makes sense, but it discounts the fact that the column has stiffness running into the joint as well so the torsional stiffness of a wide flange is really nothing to consider.  If the beam tries to roll then the "continuity" between the column, cap plate, bolts, and beam-with-stiffeners will resist the rolling.

Every structural collapse that I've investigated (about 4) has been in part due to the lack of stiffeners over columns.  In one case, there were concrete columns supporting steel beams continuous over the columns.  Heavy snow (in Texas) initiated a collapse....the roof came down but there still standing were all the concrete columns...nothing but ornamental poles reaching for the sky.

The beams simply rolled off the columns and the columns punched through the deck.

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