Dear Purushotham,
Taking the tower-top or tower-base loads from FAST and inputting them into an FEA model is generally not recommend as has been discussed recently on the forum–see e.g. my post dated Feb 23, 2017 in the following forum topic: Jacket analysis using FAST and Abaqus.
I’m not sure I can offer advice on establishing similitude between a TLP and your platform. You should establish your own modeling assumptions for your own purposes.
For fixed-bottom systems, the linearization function of FAST v8 can be used to derive the natural frequencies and mode shapes of parked or operational turbine–see e.g. Eigenanalysis FAST - #35 by Jason.Jonkman.
I gave a link to the WAMIT format above, so, as long as you understand the AQWA format, you should be able to write a converter between them. I don’t know anything about the AQWA format, so, I can’t comment further.
Changing the wind speed requires you to change the wind data in the InflowWind module of FAST, as well as setting proper initial conditions e.g. rotor speed and pitch angle, as has been discussed many times on this forum.
An error regarding the “FF wind array was exhausted” has been discussed many times on this forum e.g.: Error: FF wind array was exhausted - #6 by Jason.Jonkman.
Please use “search…” in the upper-right corner before asking questions. NREL can’t offer unlimited support to free open-source software.
Best regards,