Welding Members of Different Thicknesses 1

[abusementpark]

When you are welding together members of significantly different thickness, at what point do you become concerned about stress cracking, lamellar tearing, or any other adverse effects?

For example, let's say I am welding a 1/4" thick member to a 2" thick member with fillet welds in a T-joint connection. Would you be concerned about any adverse effects due to the thickness difference? What if you are welding a 1/4" thick member to a 5" thick member? There must be some limit.

 

[Lion06]

If one of the pieces is greater than 2" thick you need to satisfy charpy V-notch requirements per AISC. I haven't done it yet, so that's all I can offer.

 

[connectegr]

I am not aware of any limits on variation of material thicknesses. As StructuralEIT notes, for large tensile forces or in selection of very thick material charpy notch toughness requirements may apply. Post Northridge, lamellar tearing of wide-flange shapes is no longer a concern. Generally stress cracking and lamellar tearing are concerns in highly restrained welded connections. These result when the detail does not allow for adequate weld shrinkage. Your example, of a fillet welded 1/4" plate, I would not consider "highly restrained" or expect significant weld shrinkage (even if the 1/4" plate was CJP welded).

There are design, detailing, fabrication, and erection considerations that must be applied to avoid problems in highly restrained welded structures. Neglecting any of these steps can cause problems.

I have attached a presentation given by Duane Miller.

http://www.FerrellEngineering.com

 

[ishvaaag]

The attached table gives the somewhat restrictive criterium of superseded code NBE EA-95 for the maximum and minimum throats of the welds (not "sizes") according to the thicknesses of the connected plates.

Since sometimes some welds fell outside those specifications, resource was made to complete penetration welds with edge preparation, that it was surmised or said, I don't remember, was allowed in all cases. In any case, except for the crack embedded entailment in fillet welds, from a thermal locked stresses viewpoint fillet and complete penetration welds are not too much different, and hence stress relief was sometimes specified, etc, always somewhat disgusting because the somewhat blurry code aspects on this.

When feasible, others divided the plate thickness in component plates to meet the table above.

 

[abusementpark]

Thanks for attachments guys!