ABSTRACT
Un-bonded fibre reinforced elastomeric isolator (U-FREI) is a device for improved seismic performance of buildings, installed at the interface of foundation and superstructure without any connection. Shape factor, defined as the ratio of the loaded area to load free area of a rubber layer and shear modulus of elastomer have significant influence on the force-displacement relationship of U-FREI. In this study, effect of shear modulus and shape factor on the performance of prototype U-FREIs is investigated by experiment and FE analysis. Eight prototype U-FREIs with two different values of shear modulus as well as shape factors are tested under vertical pressure and cyclic horizontal displacement. It is observed that reduction in horizontal stiffness of U-FREI with increasing horizontal displacement is due to both rollover deformation and shear modulus of elastomer. Further, peak values of compressive stress in elastomer layers of U-FREI with smaller shape factor are higher than those of U-FREI with larger shape factor.
