×
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

Wide Flange Loaded Across the Flanges

Wide Flange Loaded Across the Flanges

Wide Flange Loaded Across the Flanges

(OP)
Could someone please run through the general calcs for the loading case of a wide flange on its side with the load being applied across its flanges? The beams are being used as saw horses and I need to determine a rough rated capacity.

RE: Wide Flange Loaded Across the Flanges

Please clarify. Your description is not clear enough to allow intelligent comments.

Are you concerned with weak-axis bending of the WF beam or concentrated load capacity (like buckling or crippling)?

My best guess from your description is that you have a concentrated load that's being applied transverse to a flange that's putting the flange in compression. In this case, you'd be concerned with yielding, local buckling, and lateral buckling of the flange. Is this your situation?

DBD

RE: Wide Flange Loaded Across the Flanges

You're using structural steel beams for saw horses? You must be as strong as Anthony Clark to move 'em around!

RE: Wide Flange Loaded Across the Flanges

(OP)
Yes DBDavis,
I am concerned with the concentrated load capacity. Please elaborate on the most crucial calcs concerned with this application.

RE: Wide Flange Loaded Across the Flanges

I can think of a few applicable limit states. First, I should issue a disclaimer. I am not 100% sure what you're doing, but this is my best interpretation. I also assume that you're using typical W-shapes, not a built-up slender member with really wide, skinny flanges. I also assume that you're not putting humongous loads on there.

1. Flange yielding limit state, similar to the web yielding limit state given in Chapter F of the 3rd Edition LRFD Spec. You just don't have a k part of this equation to help increase your bearing length. tw would be replaced by tf in your case. N would be whatever length of bearing you have for your condition.

2. Flange crippling, similar to web crippling in Chapter K: I have no clue how to check this and think that check #3 should cover this.

3. Lateral buckling. You also have to invent this calculation. I think your KL/r ratio is small, but might not be, depending on the slenderness of your flanges. Use K=2 and L=bf/2, r=0.29tf. Use Table 3-36 or 3-50 as applicable to come up with your stress. The A is the part you must invent. In reality this is a plate buckling problem, but we don't wanna get into that. You could define a little length of your flange as the column width, call it w. Then A=tf*s and phiPn=0.85*Fcr*A. Hopefully this is about 18x bigger than your load....

4. While not definitive, I'd make sure that my bf/2tf ratio was stocky. I know of no other way than to make sure it's less than lamba_p given in the Chapter B table.

I hope this helps.
DBD

RE: Wide Flange Loaded Across the Flanges

Will this involve a moving concentrated load?  If necessary can you reinforce the flanges with stiffeners?

You need to check local instability of your section with the AISC limits and adjust the section properties as necessary.  With weak-axis bending of a wide flange lateral-torsional buckling is not a concern. Mn=FySx or Mp=FyZx

From here you may or may not need to reinforce your flanges in the vicinity of the concentrated load, depending on the size of the flanges and the load of course.  The closest design criteria I can find for a compressive force on your flange causing instability is K1.5 in the AISC 3rd LRFD.  If you check using this equation and have a very large factor of safety, say 10 for instance, you're probably all right but who really knows.  It may prove easiest to just reinforce the flanges and be done with it, which is probably a good idea if you are looking at very heavy loads.

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