Elastomeric Seismic Isolators Behavior at Different Pads Thickness

A seismic isolator has the main function to be extremely deformable for horizontal forces, but at same time sufficiently stiff when loaded with vertical actions. These properties may be strongly influenced by both the isolator geometry (i.e. overall dimensions, number and thickness of rubber pads and steel laminas) and the mechanical properties of rubber pads. Mechanical properties of the pads, especially Young modulus, may be evaluated as a function of hardness, by means of consolidated empirical formulas. In this work, the influence of rubber pads thickness and hardness on both vertical and horizontal stiffness of realistic seismic isolators is discussed. Three full 3D Finite Element models referred to three different seismic isolators having different slenderness are analysed in detail in both vertical compression (elastic analysis) and simple shear in large deformations. Uniaxial and shear response of the seismic devices obtained numerically are finally critically compared, with the aim of evaluating the best compound to be used in practice.