Transverse Web Stiffeners for Rotation?
Transverse Web Stiffeners for Rotation?
(OP)
As seen in the example attachments, several engineers in the utility industry (where members experience significant moment/torsional loading) believe the use of stiffeners assists the overall structural design. It is believed, on the other hand by myself and few others that stiffeners do little in terms of preventing or limiting rotation at all, and create excessive fabrication work (i.e., welding of 12+ stiffeners on each beam). Also, even if stiffeners had been placed under the load centers, they are not bearing. Another place that excessive stiffening is thought to be used is in the column to top-plate area. My thought is that it may have originated as “flange stiffeners”, for which I do not see calculations on how to dis-prove their need. It has been such a legacy practice that the misconception continues. I am interested in your views. Thanks.






RE: Transverse Web Stiffeners for Rotation?
RE: Transverse Web Stiffeners for Rotation?
For flexural stability read the theory behind LTB and it's pretty clear.
For torsion, the shear stress due to torsion is not travelling around the section in all the length of the beam but maybe it's helping a little.
Stiffners are useful for limiting the buckling associated with shear of the web and also to restraint the flanges Under concentrated loads.
Here is a Q&A from modern steel:
Transverse Stiffeners as Stability Bracing
It seems that full-depth transverse stiffeners prevent rela-
tive movement of a beam’s flanges. Can the location of
transverse stiffeners in a beam be considered a brace point?
We receive this question on a regular basis. The answer is
no. Transverse stiffeners are simply along for the ride as the
section rotates and provide no resistance to lateral-torsional
buckling on their own. As a result, they do not affect the
unbraced length of the beam, Lb. Stiffeners can be used to
reduce the web deformation and improve the efficiency of
torsional braces. However, used alone, web stiffeners are inef-
fective in enhancing the stability of members.
Bo Dowswell, PE, PhD
RE: Transverse Web Stiffeners for Rotation?
RE: Transverse Web Stiffeners for Rotation?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Transverse Web Stiffeners for Rotation?
To be on the safe side, I modeled a portion of one of the beams (including the stiffeners) in STAAD using all plate elements. The results showed that not only did the stiffeners have virtually no impact on the amount of rotation......but also, very little force developed between the stiffeners and the flange (or web) from the torsional forces.
That being said, I do typically include stiffeners where I have a torque applied......if nothing else, it helps to "get it into" the whole beam.
RE: Transverse Web Stiffeners for Rotation?