Shear stiffness for elevated water tank

[Sadeq]

Hello,

I just have simple question regarding shear stiffness for elevated water tank,
this tank is elevated on a column and this column is fix in the base
my question is which formula should i use to calculate k
k=3EI/L3 OR 12EI/L3
i know the the first for fix pin case and the second one is for fix fix case

the solution for the example as far as i see , is consider 3EI/L3

but i am trying to compare this to one floor rigid slab example in which the solution is 12 EI/L3

So why the tank is different, could nay one guide me through this

 

[Valkarie]

Thank you The shear stiffness calculation for an elevated water tank is based on the type of support it has at the base. If the tank is supported by fixed columns, then the equation 3EI/L3 should be used. If the tank is supported by a rigid slab, then the equation 12EI/L3 should be used. The difference between these two equations is that the first assumes that the columns are fixed and the second assumes that the slab is rigid.