Do, E, P, t, and ts are as defined in UG-28(b).
The adequacy of the moment of inertia for a stiffening
ring shall be determined by the following procedure.
Step 1. Assuming that the shell has been designed and
Do, Ls, and t are known, select a member to be used for
the stiffening ring and determine its cross-sectional area
As. Then calculate factor B using the following formula: