Performance Evaluation of bi-directional Roller Bearings for Seismic Isolation of Buildings Under Near-fault Earthquakes

An advantage bidirectional sloped rolling type isolation device composed of multiple rollers in both orthogonal-in-plane directions is studied in this research. The analytical model of a single direction of roller bearing (RB) system is extended to a two-direction RB system. Also, a 3D linear-elastic frame element to build the finite element model is used to incorporate the response of the building model. Several experimental tests of a physical building model with and without an RB system are used to validate the numerical model. The model is used to assess the nonlinear response history analysis of a four-story multi-column building system with two different physical properties that represent buildings with low and high lateral stiffness when subjected to pairs of scaled near-fault earthquake records. The effect of the angle of inclination of bearing plates in the range of 1.0 o to 4.0 o and sliding friction force is also investigated in a parametric analysis to evaluate the performance of RB with supplementary damping mechanisms ranging from 0.0 to 0.5N/kg, i.e., friction force normalized with the structure mass. Results show that the proposed bi-directional RB system is suitable for reducing the seismic response of rigid and flexible multi-column structures. In particular, the RB system reduces structure acceleration responses by 5–85% in the flexible structure and 86–96% in the rigid structure. Furthermore, an angle of inclination of bearing plates greater than or equal to 3.0 o is an advantage to ensure the self-centering capacity.