Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Lateral Support

Status
Not open for further replies.
121202

121202

Chemical
Joined
Dec 12, 2002
Messages
36
Location
GB
What constitutes lateral support to prevent lateral torsional buckling in steel I-Section beams?

For example, is it adequate to provide transverse stringers connected to the compression flanges of parallel beams, i.e. to provide a grid structure? If that is acceptable I presume that you would then only need to check the spans between stringers for buckling?

Alternatively if steel plate was placed on the top of parallel beams and welded to the compression flanges would that be adequate? Would it be permissible to then ignore lateral torsional buckling in the analysis of the beams?
 
Sort by date Sort by votes

Torsional buckling occurs when the whole section rotates in between the lateral supports.

Yura does a great lecture on the subject. AISC sponsers the lecture from time to time.

Usually when I provide transverse stringers and bolt into the web of the beam needing lateral support, since it cannot rotate, I consider that fully lateraly braced.

A steel plate welded to the top of parallel beams also does a good job of providing lateral support, however the field will want to just lay the plate across several parallel beams without having to go in and make overhead welds between the plate and beam. Just make sure that weld is made.

Regards,


JPJ


 
Upvote 0 Downvote
Check out this thread from a couple of months ago.


If a grid is constructed but the braces are not connected to some sort of lateral system such as a roof or floor diaphragm, the beams may not buckle individually but may instead buckle as a group. The thing to remember about bracing besides providing the proper strength and stiffness is that the force must still be taken to the earth.
 
Upvote 0 Downvote
This is somewhat related to the issue, but is there an easy way to graph the allowable bending moment in a steel beam with Lb>Lu?. The AISC Manual has the graphs included, but is there a source somewhere that shows how to plot those graphs exactly, mathematically?
 
Upvote 0 Downvote

The graphs are based upon the mathematical equations F1-6, F1-7 and F1-8 in Chapter F of the AISC Specification.

Look on page 5-47 of the 9th edition AISC Manual if you are using the ASD method.

Regards,

JPJ
 
Upvote 0 Downvote
thanks Virtual
Someone had snatched my 9th Edition, and I didn't see anything in my 8th Edition. Rather than spend my free time playing video games, I am developing an Excell spreadsheet to design steel beams. (Except when my wife asks me to watch "ER" with her).
 
Upvote 0 Downvote

Look under Specification section 1.5.1.4.5

I don't have my "red" manual with me but my "green" manual refers back to this section for the "Members with Compact or Noncompact Sections with Unbraced Length Greater than Lc".


Regards,

JPJ
 
Upvote 0 Downvote
thanks again Virtual...same formulae on p. 5-22 of the "red', except limit of <=0.60Fy was not included (obvious ennyway).
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

hoshang
  • Question Question
Truss Top Chord Lateral Support
2
Replies
31
Views
41K
hoshang
hoshang
SocklessJ
  • Locked
  • Question Question
Tall brick veneer lateral support
Replies
14
Views
8K
XR250
XR250
D
  • Question Question
Mixed Lateral System
Replies
4
Views
10K
human909
human909
F
  • Question Question
Lateral Stability
Replies
2
Views
3K
KootK
KootK
PT99
  • Locked
  • Question Question
LATERAL BRACING
Replies
9
Views
5K
KootK
KootK

Part and Inventory Search

Sponsor

Back
Top