I think that is a bad use of the "all around" symbol. The symbol, as I would read it, is that the weld goes up the sides and over the top of the cross plate (in which it is not then, technically, a fillet weld) and then down the other side.

So the author of this detail might argue that because the top is not a fillet, but a butt weld, then the all around would imply just the three sides.

Crossing a weld over a discontinuous plane is not a good idea anyway.

A preferable symbol would be a one-sided fillet with a note calling for "3 sides" if that is what the detailer wanted.

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Typical of the last 20-years or so of poorly trained engineers. Reasonably certain that the gusset is to be welded on all three sides, near-side and far-side. The eng MAY also want a seal weld applied to the edge of that gusset t the tips of the flanges. And the engineer definitely needs some further training in welding symbols, and fillet weld gauge sizes [tough to find a 0.12" gauge, but i have a 1/8" one].

I agree that the welding symbol is "all around" and I agree that the "professional" that drew the sketch could have been more precise with the application of welding symbols. However, the observation that many design professionals only do a half baked job is consistent with my 10-80-10 rule. 10% of the people excel at their profession, 80% do enough to keep from getting fired, and the remaining 10% would do society a favor if they found different professions.

The best option is to go back to the designer and ask for clarification of what welds are required. The individual was paid to perform a service. He failed to fulfill the bargain and should complete the task by being more complete in specifying the welds.

Best regards - Al

if it has the all around circle then the welds all four sides, all around