The purpose of this work is to present a general framework for the computation of time responses of viscoelastically damped systems, by using recurrence formulas involving internal variables into a time discretization scheme. The most common viscoelastic models are studied, and especially the four-parameter fractional derivative model. After presenting the numerical methodology adapted to the representation of the constitutive behavior, the proposed approach is applied to the computation of time responses of structures treated with constrained viscoelastic layers.