Dear Baoxuan,
Normally, you can assign a very large value for “torsion stiffness (TWGJstff )”, “axial stiffness (TwEAStff )”, and very small value for “fore-aft inertia (TwFAIner )” ,“fore-aft inertia (TwFAIner )”, “side-to-side inertia (TwSSIner )”. It will not influence the results, as discussed in below link.
https://forums.nrel.gov/t/blade-mode-shapes-with-bmodes/1441?u=ran.tu