Tower top loads estimation for substructure design

Dear all,
I want to try out new floating substructure design coupled with wind turbine. I have read a similar thread regarding this (jacket substructure designing): http://forums.nrel.gov/t/jacket-analysis-using-fast-and-abaqus/1558/1.
I had few questions regarding estimation of tower top loads and forces:

  1. Is it fair to use the loads of tower-top from FAST as an initial estimate of above-sealevel structural load for AQWA or any other FE software (for design of floating/underwater substructure) ?
  2. I am using FAST v8.16 and Test18.fst. As far as thrust force experienced by the tower-top structure, which output parameter would be useful, LSSGagFxs or YawBrFxp?

Thank you! :slight_smile:

Dear Tiasa,

I would expect the floater-induced motions of the rotor-nacelle-assembly (RNA) to impact the tower loads. So, if the floater motions are not accounted for in your FAST simulations, the tower-top loads may be underestimated.

Often the low-speed shaft (LSS) gage is placed at the main bearing, in which case LSSGagFxs represents reaction force along the LSS at the main bearing, or in other words, the mechanical thrust transferred from the rotor to the drivetrain and nacelle. YawBrFxp represents the fore-aft reaction force at the yaw bearing, or in other words, the mechanical thrust transferred from the nacelle to the tower. Both are useful, depending on what loads you are interested in.

Best regards,