Hi peter

 I tried the Structural Transient, because it allows frication contact between the rail and the sleepers

the BC for the sleepers (bottom face ) I have put a displacement on the sleepers and made it free in all directions except Y direction to simulate its BC in the lab, and also simulate the hammer impact using nodal force,  the solution took 9 hours to finish and the result was not realistic, when I play the animation video the rail was flying away from the sleepers, I copied the time domain result (time S vs Acceleration mm/s^s) and then using MATLAB to get FFT

the results was completely unrealistic