cantilever beam modelling

My requirement was to do modal analysis of a hallow tank fixed at the bottom, which is of same thickness

hence it will behave like a cantilever beam of cylindrical cross-section.

So I modeled beam in space, with the cross sectional properties equivalent of tank.

Tank data:

OD : 4.334m

 ID: 4.250m

Thickness of shell : 0.042m  

length : 22 m

POISSON 0.3

DENSITY 325.3 kN/m3

Now for the beam model I gave the cross section properties as below calculated 

Ax &  Az (= π/4(do²-di²)) ,

Ixx  &  Izz. (=π/64(do⁴–di⁴ )) ,

While analysing  I am getting error  as IY  missing for elements.

What is the Iyy value I need to specify??? 

Pls. help me out