Hirak,
There is something that concerns me regarding part 4 Section II paragraph 13 of IS-1893. This paragraph states that a consideration in using this Code is that "the mass and stiffness is more or less uniformly distributed along the height." In some vessel designs this may be the case, but in many other cases, this may not be true.
Note also in Section 17 Design Shear Force and Moment that this method works out a single equivalent force that is then used to obtain the moment at the base of the structure. PV Elite must be able to determine a seismic shear force at each level of interest. It seems that this method is somewhat simplified and does not lend itself to what is required for a complete analysis.
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Scott MayeuxCADWorx & Analysis Solutions
Intergraph Process, Power, & Marine