Dear Anuj,
As I stated above, the platform load outputs from FAST (PtfmFxt through PtfmMzt or PtfmFxi through PtfmMzi) include the combined contribution from mooring loads, wave-excitation loads, added mass, radiation damping, hydrostatics, and viscous drag. Loads from the wind turbine and tower don’t directly contribute to the platform loads, but they do, of course, have an indirect effect. For example, the rotor thrust will cause the floating platform to move; the mooring loads, added mass, radiation damping, hydrostatics, and viscous drag all depend on this motion.
When you ask about gravity forces, are you referring to the body weight of the floating platform or something else? The body weight is not included in the platform load output, but of course, the body weight does contribute to the overall system response, and so, has an indrect effect on the platform load outputs.
I hope that helps.
Best regards,