Rubber products are widely used in order to isolate severe vibrations or strong earthquakes. Rubber materials have strong nonlinearities in dynamic and static stiffness properties. Actually, when engineers plan base isolations or vibration isolations, these nonlinearities are approximated as linear. Mullins effect is known as one of strong nonlinear characteristics. Rubber materials subjected to a series of loadings cause stress softening associated with the Mullins effect. It is important for engineers to apply an appropriate and easy analysis method to estimate isolation performances taking account of stiffness softening caused by the Mullins effect. In this study, rubber materials were modeled by two approaches with consideration of stiffness softening caused by the Mullins effect. The FEM analyses to represent the behavior of columnar rubber isolators were conducted. The aptitudes of both approaches and how to model rubber materials for base isolations and vibration isolations are described.

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