TheEverest (Mechanical), this should not be the way.. I think you need the services of experienced engineer on the this subject.
The formulas to calculate those stresses namely meridional membrane stress and circumferential design stress are analytic not empirical.
Just for sharing the knowledge,
You can use the formula ( E.6.2.2.1 Shell Compression in Self-Anchored Tanks) for seismic case, and for wind , you can use the same formula by using M for wind instead of Mrw and put Av=0 .
Regarding circumferential stress , look to the previous threads .