AISC's Reduced Allowables for High b/t ratios

[tmschrader]

Hello

If b/t ratios are larger then those in the various sections of 1.9 then a appendix must be used to reduce the allowables. I have been checking older editions 7 and 9. In edition 7 the formula is on page 5-115 to 117. Does the more recent AISC appendix or any other code document Allow for increased allowables if stiffeners, return bends or grooves are used in the compression plates. I have a SSAB document that allows this but does not reference any European codes that support this.

The AISC increased allowables can be quite small for higher Yields of HSS. In this case increasing the Yield from 60 to 120KSI, only increases the allowable by 33%. As it does not account for improved properties from return bends or other types of corrugations.

Thanks for any input.

Note this thread brances off from a orginal thread where the accuracy of buckling programs was being asked about for local buckling. This question specifically addresses the AISC so I moved it here.


Ref:

https://www.eng-tips.com/viewthread.cfm?qid=456881

 

[JoshPlumSE]

I don't think AISC has anything like that in the specifications. However, have you considered looking a the AISI code? That's really meant to handle thin cold formed sections with high b/t ratios. It gives a lot of consideration to intermediate stiffeners and such.

Not sure if it applies to high strength steels or not. But, it's probably got a better chance to do what you're talking about.

 

[ajh1]

In AISC 360-16 Section E7 would be applicable for compression loading while Sections F3 through F5 would be applicable for flexure depending upon which elements are deemed slender.

 

[JoshPlumSE]

Ajhi -

I think he's looking for something where adding a return / bend / stiffener in the element with a high b/t ratio will increase the capacity of the member.

 

[271828]

As JoshPlum suggested, AISC doesn't have anything for this, but AISI does.

In AISC Land, there are two kinds of elements: stiffened and unstiffened. Partially stiffened, edge stiffened, intermediate stiffened, etc. aren't covered.