Table J2.4

[JStructsteel]

I want to ask about the change in the minimum size of a fillet weld in 13th AISC. I dont have the AWS code, and was wondering about using a 1/4 plate to a much thicker plate. My minimum weld can be 1/8", but what is the preheat requirements now to weld that to say a 2" plate? If I use the 12th AISC, I would just spec a 5/16" weld, and be covered for preheat requirements correct?

 

[271828]

THis table cracks me up. It's the same as before except they replaced "thicker part" with "thinner part" so now you can have insane weld sizes. AISC did this on purpose, no doubt, but I ain't buying it. I'm going with the 3rd Ed. LRFD table on this one. I know one big name steel professor who's teaching his students specifically to use the older table also. I've seen two lab tests in which the welds sheared right off at the fusion zone, perhaps due to the inadequate small size and heat.

 

[nutte]

AWS has been doing it this way (based on thinner part) for a while. The AISC specification commentary says this is due to the "prevalence of the use of filler metal considered to be 'low hydrogen'", whatever that means. I think there may be preheat requirements per AWS that the welder still has to follow.

 

[MikeDB]

The maximum size fillet weld has been 1/16 less than the thinner part for a long time. It was even that way in my 7th edition. I don't have a newer ASD manual with me, but as I recall the text reads thinner, which is different than the table.

It has something to do with the fact the any larger weld ruins the edge of the thinner plate and then you don't know what you have.

 

[nutte]

MikeDB, that requirement doesn't apply to a T joint, with a 1/4" plate welded to a 2" plate. It applies to welds on the edge of a plate, for the reason you mentioned.