Stretch-stress behavior of elastomeric seismic isolators with different rubber materials. A numerical insight

This study presents a numerical approach to predict the macroscopic behavior of parallelepiped elastomeric isolators undergoing large deformations. The model uses experimental data fitting performed through cubic splines on several rubber compounds. A nine-constant Mooney-Rivlin model and an exponential law proposed in previous studies are assumed to evaluate the energy density of the rubber pads within a finite-element discretization of the isolator. Having a few experimental stretch-stress data for each rubber compound in uniaxial tension and/or shear, cubic Bezier splines are utilized to generate a large number of data (or metadata) containing the original experimental data. The Mooney-Rivlin and exponential law constitutive parameters are estimated through the least squares method, assuming spline interpolations as data to fit. The uniaxial and shear response of each rubber compound are numerically compared and, when possible, their capability in reproducing experimental data is assessed. Full-scale rectangular seismic isolators are analyzed. The compression modulus, Ec, the shear-large displacement curves, and the hysteretic behavior are estimated. For hysteretic behavior, the model is compared with existing experimental data by modeling rubber with a recently presented overlay viscoplastic model.