<p>A methodology is presented for developing Penetration Resistance (PR) equations for concrete materials by numerically solving a series of spherical cavity expansion problems. The solutions to these cavity expansion problems are obtained with an explicit, dynamic finite element code that accounts for material and geometric nonlinearities. This paper introduces a constitutive model called the Simplified Fundamental Concrete (SFC) model that was developed to provide a fast-running simple model with a limited number of model parameters to study the influence of material model parameters on the characteristics of PR equations. The SFC model is used in conjunction with the finite element code to develop a series of PR equations. While the primary focus is on the development of PR equations, the resulting equations are also utilized in a rigid-body trajectory code to model the penetration of high-velocity projectiles into half-space concrete targets. This model provides additional insight into the influence of material model parameters on deep penetration simulations and helps determine the level of importance of each parameter. </p>