Dear @Alberto.Utrera,
All of these terms can be inferred from the 6x6 cross-sectional mass and stiffness matrices contained within the BeamDyn blade input file: IEA-15-240-RWT/OpenFAST/IEA-15-240-RWT/IEA-15-240-RWT_BeamDyn_blade.dat at master · IEAWindSystems/IEA-15-240-RWT · GitHub. That is:
- EA is the (3,3) element of the stiffness matrix
- GJ is the (6,6) element of the stiffness matrix
- The inertial twist (relative to the twist used to define the BeamDyn reference axes) can be obtained by the (4,5) and/or (5,4) elements of the mass matrix
More information on each term of the 6x6 cross-sectional mass and stiffness matrices is available in the following documentation:
- 4.6.3. Input Files — OpenFAST v4.1.2 documentation
- The document BeamDynInput_05_2020.pdf attached in my post dated Jul 20, 2020 in the following forum topic: Simulations using BeamDyn
Best regards,