How to model a bulk structure of steel using an elastic-plastic model?

[Ohama]

I am using FLAC to model a bulk structure of steel impacted by a boulder. My aim is to find out where would be more likely to have over-yielded zones.
For the steel, the available material parameters are the young modulus, passion ratio, and yield stress.
I used an elastic- plastic model (mohr-columb for the plasticity) by assigning: elastic modulus (bulk and shear), tensile strength (=yield stress), and cohesion (=0.5 x yield stress) to simulate the steel behaviour. Friction was assumed to be equal to zero.

Does it make sense to model such a bulk structure of steel using an elastic-plastic model as I did?

Thanks