Final Min Shear from Rho

The design example is jacked up. They used "cover" instead of "core". The area of the cover, in plan, would be Ag-Ac = 330 in^2 - 240 in^2 = 90 in^2. However, that's still the plan area of the cover, not the cross section of the concrete corresponding to the cross sectional area of the reinforcing. That cross section is a vertical cut, so the concrete area under consideration has a height equal to the pitch of the spiral and a width that goes across the diameter of the column.

I can't completely reconcile the rho with the area of concrete, but it's in the ballpark.

In the example calculation, the result is a #3 spiral at a 1.606" pitch. Maybe follow their calculations all the way through and see if you get a more reasonable answer.