Instruction for the Seismic fast version

Wind & Water Computer-Aided Engineering Software Tools
24

Dear @Kashyap.Subham,

If I understand your equation, this is equivalent to the following (changing notation a bit):

[M]{xsdd} + [C]{xsd} + [K]{xs} = [C]{xgd} + [K]{xg}

where xs is the structural displacement and xg is the ground motion. This is the equation used by the Seismic module of FAST v7. Given the equation [M]{xsdd} = {f}, The user-defined platform (UserPtfmLd) and tower loading routines (UserTwrLd) in FAST v7 expect that you’ll provide a force {f} applied to the platform reference point for UserPtfmLd or each tower analysis node for UserTwrLd. Rearranging the equation above, this implies that:

{f} = [C]{xgd-xsd} + [K]{xg-xs}

Now, to answer your questions:

  1. See above. The UserTwrLd routine in FAST v7 will be called once for each tower analysis node. There is logic already within UserTwrLd_DS.f90 to ensure that loads are only applied to nodes below the seabed.
  2. See above.
  3. I’m not sure I understand what you are asking, but assessing the motions of the tower analysis nodes and structural reactions at the tower analysis nodes sounds important.

Best regards,

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