i am specialized in design of steel antenna tower
i dont think sap is suitable for this kind of structures.
because you need first to determine the wind load on structure according to eia/tia specification,then determine the wind load on dishes and other ancillaries,
in my opinion the best softwares for these structures are:
mstower---risa tower---tower---staad x tower v8i
dont forget to read carfully the eia/tia speciffications