Web Stiffeners

[PEinVA]

We have some steel where the fitted stiffeners are 5" away from where we'd like them (in a number of beams, the smallest being a W14). I have been looking through the code to find if there is a criteria for how close the stiffeners should be to the anticpated load.

The stiffeners are for web crippling, and not flange bending, so I was curious as to the allowable distance away. Obviously the force distributes throughout the web, so I wasn't sure if there was a limitation on this.

Thanks for your help!

RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[PEinVA]

Also, in most of Chapter K, they refer to K1.3 thru K1.7 to be checked if compressive load....etc., if I have tension only, then I don't need to check these correct?

Thanks!

RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[271828]

How long is the bearing length? Is the stiffener on the bearing surfact at all?

 

[nutte]

Some of the checks are for both tension and compression, and some are just for one of the two. Each section spells out which ones apply.

 

[PEinVA]

The bearing surface is located 5" from the stiffeners.

They do not overlap at all.

Again this is only for a tensile load. Having a stiffener at less than 0.5d away from the load should still help using a 2:1 load distribution, right?

RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[PEinVA]

K1.2 - Local Flange Bending - Tension
K1.3 - Local Web Yielding - Tension/Compression
K1.4 - Web Crippling - Compression
K1.5 - Sidesway Web Buckling - Compression
K1.6 - Compression Buckling of Web - Compression
K1.7 - doesn't really apply here.

So only K1.2 and K1.3 apply correct? I did miss K1.3 in my previous post.

What about having stiffeners at a distance away from the load?

Thanks.


RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[graybeach]

When you say bearing surface, do you mean hanging surface? If web crippling is the problem, how is your load in tension?

 

[graybeach]

If you are hanging a load from a plate welded to the flange, the stress will be maximum at the top of the fillet and will be spread over a distance something like N+5K. The stiffener will not participate if it is outside of that. Also, for tension in the web, a stiffner will not help at all (and maybe even hurt) if it is not welded to the flange.

 

[PEinVA]

Where are you getting the N+ 5k value?

RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[graybeach]

N+5K is the distribution length in the AISC code equations for web local yielding, for a load applied greater than d from the member end. You can also find this same length in Blodgett's Design of Welded Structures (page 5.12-32 for example).

 

[PEinVA]

Right, N being the weld size and 5k for further than d from support and 2.5k for less than d. Is that in each direction or a 1.25k in each direction?

RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[graybeach]

Not sure about the 1.25k in each direction. I guess you could assume that if you physically have that distance.

 

[nutte]

No, the 2.5k is in each direction. If you're not near the end of the beam, you have 2.5k on each side, or 5k. At the end of the beam, you only have 2.5k one way, so that (plus your N) is the appropriate length.

Actually, instead of loads applied at "d" from the end, we should be looking at loads applied at "2.5k" from the end. The black HSS connections manual has an example where they use the actual length available in that direction (not to exceed 2.5k), even though the load is applied within "d" of the end.