The connection stiffness matricies are with respect to the COG motions of the connected structures. To manually create these matrices from the hinge connectors' properties and to assembly them into the required input is a hard work.
Alternatively, aftering running Hydrodynamic Diffraction, please try to run Hydrodynamic Response with the joint definitions -> Analysis Settings -> Computation Type as Freuqency Statistical Anlayis, with a definition of an irregular wave in the wave direction you want your RAOs to be calculated, the amplitudes of the RAOs can be displayed. The amplitudes and phases of the RAOs are listed in (your project)/FREQUENCY.LIS.
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