An analytical model for simulating the critical behavior of elastomeric seismic isolation bearings

Elastomeric bearings are one type of seismic isolation devices widely used in practice. Under simultaneous lateral displacement and vertical compressive load, the shear force of an individual bearing might reach a maximum beyond which the tangential horizontal stiffness becomes negative. This behavior, referred to herein as "critical behavior," has implications for the earthquake response and stability of isolation systems composed of elastomeric and lead-rubber bearings and yet is not adequately considered by widely used bearing models for numerical earthquake simulation. Semi-empirical bearing models that are able to simulate the critical behavior have been developed and shown to simulate the experimentally observed response of elastomeric bearings with reasonable accuracy. However these models rely upon numerous empirical parameters that must be experimentally calibrated and/or have complex solutions making the models impractical for design purpose.;This study aims to evaluate existing semi-empirical bearing models to elucidate the underlying mechanism(s) leading to critical behavior and to use this knowledge as guidance for the development of an improved analytical model for simulating such behavior that does not rely upon experimentally calibrated parameters. Experimental data from past and present physical testing are being used to evaluate the capabilities of the improved analytical model for simulating the behavior of elastomeric bearings and isolation systems.