SEISMIC RELIABILITY ASSESSMENT FOR YIELDING BASE-ISOLATED STRUCTURES

The aim of this work is to evaluate the seismic reliability of base-isolated systems with friction pendulum system (FPS) devices considering both isolation devices and superstructures with a nonlinear behavior. These systems are modelled by means of 2dof nonlinear models considering both a hardening and softening behavior for the superstructure and a velocity-dependent rule for the FPS. The systems are designed according to NTC08 considering a wide range of structural parameters and a set of natural seismic records scaled to the seismic intensity corresponding to life safety limit state for L’Aquila site (Italy). The yielding proprieties of the systems are valuated considering different values of the strength reduction factor and of the post-yielding slope. Then, incremental dynamic analyses are performed in order to evaluate the seismic fragility of both iso-lation level and inelastic superstructures assuming various limit states. Considering the seismic hazard curve relative to L’Aquila site and using the convolution integral, the reliability curves of the inelastic base-isolated systems, with a design life of 50 years, are derived.