Base Ring Design for Vertical Skirt Supported Vessel

According to brownell & young design the value of Ft comes greater than Fc

As, Ft = (Mwind - Wdw zd)/jd (eq.10.24)

Ft + Wdw - Fc = 0

i.e Fc = Ft + Wdw

so, Ft > Fc one can guess from above equations,

Now my query is the opposite result get from PV elite report, i.e, in report we get lesser Fc value compare to Ft.

Anybody can explain who have good hold on PV elite software.