×
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

Strehgthening of Existing Steel Column

Strehgthening of Existing Steel Column

Strehgthening of Existing Steel Column

(OP)
When enhancing the capacity of the existing wide flange steel columns by welding plates flush with the flanges of the column, do I need to consider any reduction in KL/R of the stiffened section for calulation of Fcr?? I am not sure as to whether the modified KL/R equation for built-up members is applicable in this case. Any guidance in this regard is greatly appreciated. Thank you.

RE: Strehgthening of Existing Steel Column

Short answer:
Yes

RE: Strehgthening of Existing Steel Column

(OP)
JedClampett -

Thanks for the clarification. Now, for the evaluation of separation ratio to be used in the calculation of modified KL/R, what does the term "h" mean. Is it the distance between the centroids of the plates being welded??

RE: Strehgthening of Existing Steel Column

If you add plates flush with the flanges, Rx increases so KL/Rx decreases.  You may consider it, but are safe to ignore it.

Depending on the size of added plate, Ry could increase or decrease.  If it decreases, KL/R increases and you need to consider it.

Perhaps it is best to provide a sketch showing what you intend to do.

BA

RE: Strehgthening of Existing Steel Column

(OP)
Apologize for the typo....I actually meant "modification of KL/R" when I said "reduction of KL/R". My question was regarding modification of KL/R of the stiffened section for not providing contiouous weld. Thanks again.

RE: Strehgthening of Existing Steel Column

(OP)
I intend to add plates flush with the flanges and use stitch welds instead of providing continous weld.

RE: Strehgthening of Existing Steel Column

I was assuming your r would go down and kl/r would go up.  If kl/r lower you probably shouldn't change your allowables.  If it gets higher, use the lower allowables.

RE: Strehgthening of Existing Steel Column

With only stitch welding, I would definitely use the lower allowables.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Strehgthening of Existing Steel Column

question about stitch welding plates on column,

is this applicable also regardless of the failure axial or moment?

the way i understand it if it's axial failure it should be continues weld to have continues increase in area

RE: Strehgthening of Existing Steel Column

(OP)
Thanks for the responses.


delagina-

That's where the modified KL/R comes into picture. The KL/R calulated based on the assumption that the whole section acts as a single unit is modified for welds not being continuous. This is addressed in the "Compression of built-up sections" part of the AISC manual. That is where I am stuck now....having hard time interpreting the term "alpha" in the equation E6-2. The AISC manual calls it separation ratio.

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