INFLUENCE OF DESIGN PARAMETERS ON THE SEISMIC RELIABILITY OF BASE ISOLATED SYSTEMS

Seismic isolation is considered an effective solution to protect buildings and reduce seismic losses. However, the reliability level achieved by code-conforming base-isolated structures can be not uniform due to the different behavior of the most used isolation bearings (elastomeric or sliding bearings) as well as the different design choices that strongly influence the seismic reliability of base-isolate structures. In this paper High Damping Rubber Bearings (HDRBs) are considered and a parametric analysis is performed to assess the overall reliability of base-isolated buildings designed according to Eurocodes and Italian seismic codes. In particular, the case of ordinary residential buildings is considered, and the following parameters have been considered and varied, within the range of most common values: the bearings design shear deformation and the superstructure design over-strength ratio. Probabilistic analyses are performed using a robust direct simulation approach (Subset Simulation) and a bidirectional stochastic ground motion model. For each case analyzed, results are provided in terms of demand hazard curves of the most relevant response parameters characterizing the isolation system and the superstructure.