A Hertzian contact problem is a a nonlinear contact model so we need to model the contact in detail in order to capture the pressure distribution . So this is not simple and can ofcourse not be represented by nodal forces.


Now if you have a truck driving over a bridge so you want to see the global response (deflection due to moving load) and do not care about the local pressure distribution on the deck, then yes we can just use an equivalent force for the truck that moves over the structure.


So if we care about the local stresses under the contact, then that needs to be modelled in detail with contacts. If we do not care and we care about a global response like for the bridge than a point force is fine.