Hi Noel Tan!!!
Don't forget about the the single flare-bevel, or a single flare-vee (AWS A2.4, figure 20 on pages 36&37) also... If David 2 is the person I'm thinking of, then he should consider referring to both AWS A3.0 & A2.4 in their most current versions because there is a figure in A3.0 that also shows two reinforcing bars with their ends connected along their axis to form a butt joint... in addition to this, attached to where both members of reinforcing bar meet, and beyond - is what's called: "Split pipe backing" (Figure 12, page 61)... in order to weld the split pipe backing to the reinforcing bars, one needs to deposit fillet welds to join the split pipe backing to the reinforcing bar... However, not being one that works with re-bar like David 2 does... Does one also have to deposit a groove weld to join the two re-bar members together along it's axis prior to applying the split pipe backing???
Respectfully,
Henry