Dear @Lin.Yang,
I agree with your equation for BeamDyn_Oop and BeamDyn_Inp.
Regarding B1TipRDzr
, see a similar discussion in the following forum topic: Extract blade tip torsional deformation from the Wiener-Milenković parameters in BeamDyn.
I agree that a small amount of blade torsion would influence in-plane deflection more than out-of-plane deflection.
Best regards,