Mouse hole size 1

[corus]

With gusset plates I've heard that it's better to weld the gusset plate right into the corner, whereas others say that it's best practice to use a mouse hole in the corner and only weld up to the edge of the mouse hole.

In terms of strength and fatigue life, what are the arguments for each case, and are there any recommended guidelines on the size of the mouse hole, etc. In this particualr case the gussets are to be replaced and so the existing flange weld will remain.

corus

 

[MintJulep]

I would say it depends.

I think the main reason for mouse holes is to avoid the need for custom fitting each gusset - especially when the corner has an existing weld bead or a radius.

If you do bring the gusset all the way into the corner, then you need to start thinking about weld details, partial vs. full penetration and what is already in the corner before you start welding.

In your particular case, you should also be thinking about how wide the HAZ from the existing welds might extend.

You're putting in a gusset because it's a high stress area (at least if you're actually designing gusset locations, and not just shotgunning them), so it's self defeating to add a gusset but build in a crack with a poor weld detail.

 

[Cockroach]

I would think the hole size depends on the size of the "mouse". A fat mouse, use a big hole, a skinny mouse, use a smaller hole.

But rats are different. I'd say 25% over maximum belly (hoop diameter?) diameter!

The devil made me do it...couldn't resist......

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[corus]

Given it's an average size mouse then, is it better to start/stop the weld within the mouse hole, or at the end of the fillet, or run the weld away from the gusset where the stop/start is less likely to cause cracks.

corus

 

[stfgrizz]

I was a fitter and welder in a structural steel house for a little over ten years. With gussets we ALWAYS left a mouse hole in the corner. I was told by the engineers that it was for stress relief.