How to simulate damage by reducing tower stiffness?

Wind & Water Computer-Aided Engineering Software Tools
17

Dear @Meng.He,

Here are my responses:

  1. Looking at Pietro Bortolotti’s GitHub repository for the BModes model of the IEA Wind 15-MW RWT: IEA15_BModes/RNAon at master · ptrbortolotti/IEA15_BModes · GitHub, I see that his tower top-properties differ from yours, so, how did you obtain your values? Pietro’s model is for a cantilevered tower (hub_conn = 1), so, Modes 1 and 2 are the first side-side and fore-aft bending modes shapes and are a reasonable natural frequency (not Modes 6 and 7, which are higher modes).
  2. When calculate the tower mode shapes in BModes for a floating system, hydro_M should be the added mass matrix, hydro_K should be the hydrostatic stiffness weight (accounting both for buoyancy and full-system weight), and mooring_K should be the mooring system stiffness.
  3. You should be able to interpret the modes by plotting the shapes and by their natural frequencies, assuming that you have a reasonable idea what modes to expect (surge, sway, heave, roll, pitch, yaw, tower-bending, etc.)
  4. sec_loc, mass_den, flp_stff, and edge_stff in BModes should match HtFract, TMassDen, TwFAStif, and TwSSStif in the ElastoDyn tower file. The other values in the BModes tower file (str_tw, etc.) should be set to to ensure they don’t have an effect on the solution, e.g., as I describe in the following forum topic: Consistency between Bmodes and MBC.

Best regards,