For the purpose of oil stockpiling, floating oil storage system is remarked as one of the methods of oil storage. In this report numerical simulation method of motions and mooring forces of a rectangler floating body in waves is proposed and evaluated.
　In this report two computation methods of wave forces and radiation forces are compared. One is 3-Dimentional Method (Method A) and the other is modified 2-Dime
ntional Method (Method B). In the case of floating oil storage tank, wave forces and radiation forces are almost the same between two method. And Method B is easier to use and its computation time is shorter than that of method A. Accordingly, Method B is chosen as a numerical simulation method in this report.
　Numerical results are compared with these of model experiment carried in this institute. Computed values agree well with experimental values by correcting radiation forces computed from umerical method.