Nonlinear viscoelastic damper model: constitutive equation and solution scheme

A nonlinear viscoelastic solid model, comprising a combination of linear and nonlinear springs and dashpots, is developed to represent an elastomeric damper. The nonlinear constitutive differential equation obtained from the model completely characterizes the damper behavior. A method is presented to determine the spring-dashpot parameters (coefficients of the constitutive equation) from experimental data. A quartic softening spring, in series with linear Kelvin chain, is used to match experimental data. Nonlinear hysteresis cycles at different equilibrium positions are examined. The model is able to predict behavior of elastomeric dampers under dual-frequency excitations. A `two-level implicit-implicit' scheme is developed for the integration of the nonlinear damper model into a structural dynamic analysis. With the increase in amplitude of oscillatory force, the energy dissipation by the nonlinear viscoelastic damper is found to decrease, as compared to a linearized perturbation model. With increase in initial perturbation, transient decay is slower.