An Abaqus user-element for 3D behavior of unbonded fiber reinforced elastomeric isolators (UFREIs) based on macroscale computation
As a matter of fact, the utilization of detailed 3D discretization for UFREIs is computationally expensive, with results not easily achievable for macro-scale computations in the non-linear dynamic range. Therefore, a simple and representative model is paramount. Some works where a simplified numerical model of the horizontal behavior of UFREIs have been recently presented \cite{Manzoori_2016,Osgooei_2017,HABIEB_2017}, but the behavior in compression, rotation, and torsions are still important parameters not taken sufficiently into account. This section presents a comprehensive but enough simple model for a UFREI which has been implemented in Abaqus as new user element (UEL) and takes into account the most important features exhibited by such device, such as the softening and hardening effects. This UEL is very useful for full 3D nonlinear dynamic analyses of complex isolated structures to be performed in an advanced FE code (such as Abaqus), which allows taking into account material and geometric nonlinearity.
Analytical solution for 3D behavior of UFREI
In order to calibrate the mechanical properties of the proposed UEL element, a 3D FE model of a U-FREI is previously built by applying hyper-elastic and viscous behaviors for the rubber material. The geometry is presented in Figure 1. The hyperelasticity follows Yeoh strain-energy model, which corresponds to a rubber with shear modulus 0.6 MPa. While the viscous damping, that is characterized by a Prony-series, represents a rubber with 8% of damping.