Site response and liquefaction analysis have traditionally been decoupled in engineering practice. Simplified total stress nonlinear effective stress constitutive models are available for use in one-dimensional (1D) site response analysis, while several advanced soil constitutive models have been developed for use in dynamic finite difference and finite element analyses. In this study, we describe a new simplified coupled hyperbolic constitutive model with an energy-based excess porewater pressure generation capability (MRDF-u: modulus reduction and damping curves fit using a reduction factor and including porewater pressure generation, u). We then validate this model using sets of cyclic triaxial compression and cyclic direct simple shear tests. Comparisons of stress-strain, excess porewater pressure, modulus reduction, and damping illustrate that the proposed MRDF-u constitutive model reasonably captures relevant elements of the cyclic behavior of sands, but does not simulate dilation. In particular, the MRDF-u captures excess porewater pressure generation during cyclic loading and can be employed in a coupled 1D nonlinear, effective stress site response analysis to evaluate the occurrence of liquefaction in sands.