Plug/Slot Weld Strength Calc

[NBEEBE]

Hi i'm wondering if someone could clarify how the effective area of a plug or slot weld is calculated as well as run the numbers on an example slot weld (see attached) so i can cross check against what i have come up with. My assumption is that Awe is figured by the area of the slot times the depth of the slot, or the fill amount that is being specified to take place for the welded slot. Thanks

 

[Tmoose]

No atttachemtn I can see.

This document has quite a bit about plug welds. A <ctrl> F word search steps hruy every one.

https://law.resource.org/pub/us/cfr/ibr/003/aws.d1.1.2000.pdf

Area figured as the area of the hole at the faying surfaces.

 

[NBEEBE]

Sorry forgot to attach sketch. I think the depth of the slot needs to be a factor in this equation otherwise the depth wouldnt matter and the results for a 1/4" deep slot/plug would coome out looking the same as a 1" deep slot/plug, which looks way too high when you run the numbers on. I come up with ~19.25kips without factoring in the depth and 4.81kips when i do incorporate the depth. The 4.81kips seems much more realistic to me.. Do you agree?

 

[NBEEBE]

Any input on whether I'm way off base or on track is much appreciated. Thanks

 

[Ron]

It depends on whether you are calculating shear perpendicular to the plane of the slotted sheet or parallel to the slotted sheet. If parallel, consider the area of the slot. If perpendicular, consider only the perimeter of th slot times the thickness of the sheet to give you the shear area.

If you need to consider localized deformation for parallel shear, then the sheet thickness is considered (localized buckling of the sheet at the edge).

 

[humanengr]

NBEEBE,
If you're using AWS D1.1 (Structural Welding Code), Refer to Sections 2.4.5.3 and 2.4.5.4
The effective area of the plug or slot weld is generally equal to the area of the hole or the
slot being welded. This is applicable for the load putting the weld in shear.

Awe CANNOT be area of the slot X depth. That would result in a VOLUME in in3 / mm3, not area which will
give you incorrect results.

As mentioned above, if the load is perpendicular to the plane of the weld, then the weld should be in tension. I'm not aware of a Code provision for tension on a plug or slot weld. What was mentioned seems to make sense. However, instead of perimeter X thickness, perhaps a fillet weld around the perimeter of the hole or slot and using the effective throat would be more appropriate. The remaining area would then just be filled with weld. But I would confirm this is in compliance to your Code regarding tension on a plug weld. I'm not sure what qualifications may be required for such welds or tension strength of such welds.

So to the root of your question, the depth of the plug / slot weld does not go into the calculation for effective area or weld shear strength. However, the required depth of welding must be provided even though it is not directly a factor in the weld strength.

One final note; in addition to checking the weld strength, there should be other limit states related to the base metal(s) that should be considered such as bearing, tear-out, block-shear, etc. similar to what would need to be checked for a bolted connection.

 

[Tmoose]

NBEEBE ain't been back for several weeks (since Sept 15). I'm guessing he's hanging around with new friends.