ododbefar,
Be careful with your material selection. 500 MPa is not a load, it is a stress, and that is about the ultimate limit for commonly available reinforcing bars. Once you thread a bar, the load carrying capacity is reduced considerably, both from the reduced area and from the fact that the outer skin of a reinforcing bar is stronger than the centre. As mentioned above, there are manufacturers of reinforcing, e.g. Dywidag, Reid, which will accept a nut.