Thank you for your answer. I have some follow-up questions.
More specifically, in the process of finding the new floater center of mass (CM), my idea is to use the original total floater mass (17,839 t) and the original CM, since the report does not provide detailed information on the CM of each component, comprising the floater. Then, the new CM will be defined as:
CM,new= M,tot,old/M,tot,new * z,cm,old + Σ_i M,added(i)/Mtot,new *z(i) .
where M,tot,old and M,tot,new is the old and new total floater mass respectively, z,cm,old the vertical position of the old CM and z(i) the vertical position of the added mass.
However, due to the extra mass, the floater draft is going to increase from its original value of 20 m, therefore moving the floater initial CM to a more negative value. Therefore, I have to calculate the new draft. For this reason, I am trying to replicate the UMaine Volturn US-S semisubmersible platform numerical results, presented in its documentation.
According to my calculations, in case that the whole turbine+floater mass is considered (20,093 t), plus the weight of the mooring system (or vertical pretension force, according to the floater documentation), then the calculated displaced water volume is the one stated in the paper (20,206 m3). So, this is the process for calculating the new displaced water volume
However, then, I have trouble in calculating the draft. When I divide this value with the total area of the floater (3 pontoons+4 columns), I have a draft of 10.3 m, which is smaller than 20 m. Then, since the pontoons are flooded with water and thus,they do not contribute to buoyancy, in case I use only the area of the 4 columns, using a similar process as before, the calculated draft is about 50 m, which is higher than 20 m.
1.) Do you think that my rationale is correct?
2.) If yes, do you have any indication of which factor I do not consider in my calculations?
3.) Do you have a hint on what does it happen in the case I substitute the extra platform weight with less water ballast?