So you mean I have to first try remove the sleepers and replaces them with a remote displacement by splitting the bottom face of the rail  at the place where the sleepers?

Yes, that is what I mean. You don't have to do it, I just think it is a good idea because it is quick and easy compared with the next logical step.

but what about the sleepers engineering data ?

Will not be relevant to this model.

it will not be included in the model, I mean is it will be logical ? 

If the model matches the experimental data better than your first model, then it is a better model.