Dear Hamid,
BModes can be used to derive mode shapes and frequencies of blades or towers. When used together with FAST, it is only the blade and tower mode shapes that are needed. For the NREL 5-MW turbine atop the MIT/NREL TLP, we’ve already created mode shapes for FAST using ADAMS in place of BModes. So, we don’t have the BModes input files for this system. You should be able to make them yourself, but there really is no need to. If all your interest is in obtaining the natural frequenices of the TLP, you can use the linearization feature of FAST to derive them. Otherwise, these frequencies are published in Table 6 of the following report: BladedDLLInterface.
Best regards,