An experimental study on unbonded circular fiber reinforced elastomeric bearings

Seismic base isolation by introducing a flexible horizontal layer at the foundation level of a structure has proven to reduce the seismic demand. Steel reinforced elastomeric bearings have been used for that purpose extensively in the last years. More recently, innovative fiber reinforced elastomeric devices have been investigated as they bring important advantages as reduction of manufacturing and transport costs. The current article analyzes relevant mechanical properties for seismic isolation such as vertical and horizontal stiffness as well as damping capacity in fiber reinforced elastomeric bearings, focusing on the effect of shape geometry and material of the fiber reinforcement layers. Quasi-static cyclic experiments under vertical and combined horizontal and vertical load have been performed in order to investigate the effect of compression, horizontal deflection, frequency of the load and geometrical parameters. Compressive loads up to 12 MPa have been investigated. Moreover, the performance of bearings with round and square plan geometry under multidirectional loading is examined. Comparisons between the obtained results and data from previous works are discussed.