Innovative low-cost recycled rubber–fiber reinforced isolator: Experimental tests and Finite Element Analyses

An experimental study on unbounded square carbon Recycled Rubber–Fiber Reinforced Bearings (RR-FRBs) was conducted to investigate their lateral and vertical behavior, under seismic loading. These low-cost rubber bearings are innovative elastomeric bearings that employ recycled rubber and fiber as reinforcement material. They have significant advantages compared to those bearings made up of natural rubber reinforced by steel layers or fiber sheets: higher dissipation capacity, lower manufacturing cost, light weight. RR-FRBs are intended for seismic isolation of ordinary low-rise buildings located in high seismic risk regions, and are designed to be mounted with no need of bonding to the upper and lower structures. This feature allows them to deform freely, reducing, and possibly eliminating, the tensile stresses generated by shear deformations. In this work, the seismic performance of the proposed bearings is investigated by means of both experimental tests and Finite Element Analyses (FEAs). The study provides useful information on both horizontal and vertical stiffness, and on the damping properties of the isolators. Moreover, a description of the instability of the bearings is discussed. The sensitivity of RR-FRBs to lateral displacement history and vertical pressure applied on the bearings is pointed out. Moreover, the validity of easy to apply design criteria is discussed.