Platform Fatigue Analysis

Dear all,

I should make a fatigue analysis of the platform for the Hywind using the output from a FAST simulation and MCrunch. I’ve seen in FAST User’s Guide that an interesting channel could be:

PtfmMyt                 Platform pitch tilt moment

But actually I cannot deeply understand to what does this output refers. Could someone explain me if this is the loads at the platform base or top? And what does it mean “pitch tilt”?


Dear Giuseppe,

The platform load outputs in FAST v7 (PtfmFxt through PtfmMzt or PtfmFxi through PtfmMzi) are loads applied at the platform reference point (for a floating wind turbine, the reference point on the undisplaced platform will be at the intersection of the still water level and the tower centerline). PtfmMyt is the platform-pitch moment, which will causing tilting of the system. The terms included in these platform load outputs are documented in my Jan 22, 2013 post in the forum topic found here:

Best regards,

Dear Jason,

as usual you solved my problem.
Thank you again!


I recommend you use MLife for fatigue calculation rather than MCrunch. It is optimized for fatigue calculations, while MCrunch has only minimal support for them.


Dear Marshall,

thank you for the advice. I’ll see also MLife. Anyway I just need a basic analysis for fatigue, so I think MCrunch should be enough.

Best regards,

Dear all,

I am using MLife in order to have the DEL of the OC3Hywind 5 MW floating wind turbine.
I have a small question about the PtfmMyt, PtfmMxt and PtfmMzt parameters. I have not seen these outputs in FAST V8 whereas they are available in FAST V7. How can I have them as an output during my simulation with FAST v8?

Thank you in advance for your answer.

Best regards,


Dear Audrey,

These outputs have been removed from FAST, replaced with a large variety of outputs from HydroDyn and the various mooring modules.

Best regards,