Partial Depth Stiffeners for Compression Force
Partial Depth Stiffeners for Compression Force
(OP)
Hi all,
I want to design some partial depth stiffeners for a steel beam with some concentrated loads on it. Normally I'd just go with full depth stiffeners but I'm trying especially hard to be fabricator friendly this time around.
AISC J10.8, "Flanges and Webs with Concentrated Forces" ,states that FULL DEPTH stiffeners should be designed as little mini-columns with certain stipulated geometric limitations. Fine.
But how should one design a partial stiffener? Should it be treated as an even shorter mini-column? Can you ignore the buckling limit state and just design for b/t and shear transfer?
Also, does the last sentence of AISC J10.5 preclude the use of partial height stiffeners for addressing the limit state of web compression buckling? I can't tell for certain from the language and punctuation used.
Thanks!
I want to design some partial depth stiffeners for a steel beam with some concentrated loads on it. Normally I'd just go with full depth stiffeners but I'm trying especially hard to be fabricator friendly this time around.
AISC J10.8, "Flanges and Webs with Concentrated Forces" ,states that FULL DEPTH stiffeners should be designed as little mini-columns with certain stipulated geometric limitations. Fine.
But how should one design a partial stiffener? Should it be treated as an even shorter mini-column? Can you ignore the buckling limit state and just design for b/t and shear transfer?
Also, does the last sentence of AISC J10.5 preclude the use of partial height stiffeners for addressing the limit state of web compression buckling? I can't tell for certain from the language and punctuation used.
Thanks!






RE: Partial Depth Stiffeners for Compression Force
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RE: Partial Depth Stiffeners for Compression Force
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Partial Depth Stiffeners for Compression Force
http://www.FerrellEngineering.com
RE: Partial Depth Stiffeners for Compression Force
If I remember correctly, there are applications where partial height stiffeners must be used...as in fatigue applications.
RE: Partial Depth Stiffeners for Compression Force
The text reads as follows:
When required, a single transverse stiffener, a pair of transverse stiffeners, or a doubler plate extending the full depth of the web shall be provided.
I interpret that as saying that if stiffeners are required, that they must be full depth. The last line in J10.8 seems to support this.
Transverse stiffeners shall extend a minimum of one-half the depth of the member except as required in J10.5 and J10.7.
It makes sense that the stiffener would be full depth. This limit state occurs when you have compressive loads on both sides of the member. If you needed a stiffener, and you were going to use half-depth stiffeners, you'd have one half-depth stiffener at each flange, making a full-depth stiffener anyway.
RE: Partial Depth Stiffeners for Compression Force
http://www.FerrellEngineering.com
RE: Partial Depth Stiffeners for Compression Force
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Partial Depth Stiffeners for Compression Force
It escapes me right now why this is the case.
Also, I do believe there are provisions in AISC for stopping welds short of the fillet radius on wideflanges ...again the reason escapes me other than welding in the "K" regions can cause problems in heavy wideflange shapes.
RE: Partial Depth Stiffeners for Compression Force
@Connectegr: The flange/stiffener is welded for the difference between the capacity required and the critical, non-stiffened, limit state correct? Also, shear buckling is a possibility for partial height stiffeners isn't it?
@Toad: You're absolutely right. Welding into the k region near the tension flange does cause fatigue problems.
@Nutte: I agree with your interpretation. Thanks.
@Connectegr: Let's say, hypothetically that you designed a partial depth stiffener loaded from one side. However, to make the numbers work, the stiffener had to extend exactly full depth. Since the shear in the stiffener dies off to zero at the far end, would you then NOT have to design it as a compression member?
@Paddington: I'm not so sure about your statement regarding web stiffeners. From my reading of the code, and my understanding of the failure mechanisms I think that partial height stiffeners can be used to address both web crippling and web yielding.
RE: Partial Depth Stiffeners for Compression Force
1) When AISC mandates a full depth stiffener for situations where only one flange is loaded, does that mean:
a) A truly full depth (flange to flange) stiffener or;
b) A stiffener that extends to NEARLY full depth but not into the k region as discussed above.
I have seen many girders with end bearing stiffeners that were detailed as described in "b".
2) For the three web stiffening limit states (crippling, yielding, and buckling), how do you know that your partial height stiffener has successfully resolved the issue? Couldn't you have just moved your crippling, yielding, or buckling failure to the end of the stiffener rather than at the web/flange intersection? This goes back to paddington's comments above.
RE: Partial Depth Stiffeners for Compression Force
RE: Partial Depth Stiffeners for Compression Force
Is it to...
Transfer a continuous force thru the beam?
or
To stiffen the web?
Then apply limit states of chapter K in your check.
In the case of crane runways and probably highway bridge girders, I do know that, do to fatigue cracking, intermediate stiffeners should not be full depth and should not be welded to the bottom flange.
RE: Partial Depth Stiffeners for Compression Force
In your hypothetical case, I think you have to check the plates for buckling. You can stop the plate at the "k" (nearly full depth) without buckling.
http://www.FerrellEngineering.com
RE: Partial Depth Stiffeners for Compression Force
In most cases your plate thickness will be controlled by the tensile or compressive capacity of bearing area at the flange. Buckling will not control unless the beam is very deep. Bending will not control unless the flanges are very wide. Also the welds at the flanges are often larger than the weld at the web.
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