×
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

Max.allowable width of flange in box girders

Max.allowable width of flange in box girders

Max.allowable width of flange in box girders

(OP)
What is the maximum allowable width of flange between the two webs of a box girder forordinary mild steel plates and manual welding such that the entire width can be used to calculate section properties?

RE: Max.allowable width of flange in box girders

What design code governs your design?

RE: Max.allowable width of flange in box girders

I am not sure the answer is straightforward. It will certainly depend on the code used, but it should be related to flange and web thicknesses and flange stiffeners, both transverse and longitudinal.
More than the maximum width of flange, the important issue should be the effective width of flange, and shear lag calculations will give you that.

RE: Max.allowable width of flange in box girders

(OP)
Jmiec,
The code to be used in this case is indian code IS:800-86.
It doesn't clearly mention the requirements for box girder in detail. For single web the maximum flange outstand is given as 16t.Doubling it for box girder for flange between two webs , it comes out to be 32t where t is flange thickness. However in crane girders having box section i routinely find flange widths close to 50t.Thats the reason i want to find if in some reference this requirement is clearly mentioned?

RE: Max.allowable width of flange in box girders

Our old steel code limited the b/t ratio for unstiffened I shapes to 95/Fy1/2, where Fy is in ksi.  For carbon steels, this corresponds to your width limit of 16t.  

For box sections, the limit was 238/Fy1/2.  As you can see, the limit for box sections is more than double the limit for I shapes.  The thinking is that a plate stiffened along two edges is less susceptilbe to buckling than a plate stiffened along one edge and free at the other.  

A b/t ratio of 50 seems to be will into the range where the effective width should be reduced.

RE: Max.allowable width of flange in box girders

(OP)
Jmiec
can you please give the details of your code

RE: Max.allowable width of flange in box girders

The old Code I'm referencing is the 9th Edition of the Steel Construction Manual, published by the American Institute of Steel Construction.  It has been replaced by later codes, with similar, more sophisticated provisions for b/t ratios.

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