Influence of crosslinking on the seismic performance of unbonded fiber reinforced elastomeric isolators (UFREI) made of regenerated rubber

Recent earthquakes have highlighted the high seismic vulnerability of the structures and the need of retrofitting interventions. Different seismic protection strategies and techniques can be used to increase the seismic capacity of existing masonry constructions. Common retrofitting techniques are generally based on a strengthening approach. Instead, innovative retrofitting strategies can be used to mitigate the effect of earthquakes, with the aim of decreasing the seismic demand on the structure or increasing its energy dissipation capacity. One of the most innovative devices is the Unbonded Fiber Reinforced Elstomeric Isoletors. UFREIs are made of alternate layers of fiber and rubber and they are interposed between the ground and the foundation, with the particularity that no bonding or fastening is provided between the bearing and top-bottom supports. In this paper, through the FE software code Abaqus, a series of nonlinear dynamic analysis are performed to investigate the influence of crosslinking on the seismic performance of UFREI made of regenerated rubber. Numerical results show that the devices vulcanized at 130°C for 40 minutes, although having suboptimal crosslinking density, are suitable to properly isolate low-rise buildings.