Addressing local buckling of flange/webs 1

[louisz444]

A contractor wishes to use a W-section that is a class 4 section (local buckling of flanges).

They said they can weld an additional plate on the compression flange to address the b/t ratio. However, they will only be using stitch welds. How do you check what the minimum amount of weld is required such that the W-section is no longer a class 4 section? Is it simply just enough for the welds to handle the shear flow?

 

[human909]

The short answer is likely YES. (unless your additional plate is negligible)

The long answer starts getting complicated as you'll need to look at into the complexities of buckling.


But the confusing part of the question is; WHY. If you need a Class 1 or Class 2 section why not just use one? Welding plates on a Class 4 section would generally be more expensive than using a more suitable section.

 

[mfgenggear]

yes agree, use the correct hardware

 

[louisz444]

The short answer is likely YES. (unless your additional plate is negligible)

The long answer starts getting complicated as you'll need to look at into the complexities of buckling.


But the confusing part of the question is; WHY. If you need a Class 1 or Class 2 section why not just use one? Welding plates on a Class 4 section would generally be more expensive than using a more suitable section.

It's because the contractor has a bunch of these extra sections available from a previous job (unused). Supplying these sections would be considerable savings for the client. If you have sources/literature to how to check this, I would love to read about it.

Thanks!

 

[KootK]

Is it simply just enough for the welds to handle the shear flow?

That usually will suffice but your instincts are good here: there is some nuance to be considered.

 

[canwesteng]

I would just weld a pair of angles to either end of the flanges, to reduce the unstiffened length of the flanges.