Does seismic isolation reduce the seismic vulnerability and the variability of the inelastic seismic response? Large-scale experimental investigation

This paper focuses on the large-scale experimental investigation of the seismic vulnerability and the variability of the inelastic seismic response of seismically isolated structures in comparison to conventional, fixed-based structures. The experimental setup comprises a steel structure consisting of two steel columns and a steel mass on top. The structure is seismically isolated using four friction pendulum bearings and subjected to an ensemble of strong recorded earthquake ground motion excitations using the shaking table of ETH laboratory. A mechanical clevis connection consisting of two hinges and two replaceable steel coupons is designed and constructed to facilitate the investigation of the seismic inelastic behavior of the structure for the selected ground motion record ensemble through the replacement of the damaged coupons after each shaking table excitation. Within this frame, the mechanical clevis connection presented in this study facilitates the parametric and experimental investigation of the seismic, inelastic behaviour of a wide range of structures and the experimental determination of their seismic fragility curves. The seismic vulnerability and the variability of the seismic response of the seismically isolated and the corresponding fixed-based structure are compared for three seismic hazard levels. The comparison of the response of the two structures demonstrates experimentally the ability of seismic isolation to reduce the seismic vulnerability and the variability of the seismic response of structures subjected to strong earthquake ground motion excitation, thus leading to the design of structures of higher performance, predictability and reliability in their response, even for extreme earthquake events.