A Study on Experimental Shear Behavior of Fiber-Reinforced Elastomeric Isolators with Various Fiber Layouts, Elastomers and Aging Conditions

Fiber-reinforced elastomeric isolators are innovative devices for seismic isolation that employ fibers, rather than steel, as reinforcement material. Their light weight and low cost could help to widen the application of seismic isolation, to housing for example, and to buildings in highly seismic areas of the developing world. Experimental studies available in the literature have already demonstrated the suitability of fiber-reinforcing isolators to protect buildings from earthquake. Theoretical analyses have been carried out to describe the isolator behavior under compression and bending. However, no treatment of its behavior under compression and shear has been performed yet. This because of objective difficulties due to the non-linearity both of the geometry and the properties of these materials. The present paper proposes a simplified geometric model to describe the isolator’s deformed configuration under compression and shear, based on the observation of its experimental behavior. The results of compression and shear tests carried out on 17 pairs of fiber-reinforced isolators are reported. The specimens have different characteristics as regards rubber typology (neoprene and low and high damping neoprene), reinforcement (bi-directional or quadri-directional carbon fiber fabrics), shape factor, and aging (unaged and aged specimens). On the basis of the proposed model, an expression for the equivalent linear horizontal stiffness of fiber-reinforced isolators is proposed. This expression predicts well the experimental results. The predictions are more uniform and accurate than those obtained from the stiffness expression of traditional isolators, which is commonly used in the literature also for fiber-reinforced isolators.