The study evaluates the seismic reliability of isolated multi-span continuous deck bridges considering the influence of the friction pendulum isolators and provides seismic reliability-based design abacuses as a function of both the structural properties and reliability level expected. The behavior of these systems is analyzed by employing five degrees of freedom accounting for five vibrational modes of the elastic reinforced concrete pier and a single degree of freedom to model the response of the infinitely rigid deck equipped with the isolators. The reinforced concrete abutment is modelled as a fixed support. The non-linear FPS response is described also considering the velocity-dependent behavior. The uncertainty in the seismic input is taken into account through a set of natural records with different characteristics scaled to increasing intensity levels. The uncertainty on the friction coefficient is modelled through an appropriate probability density function. Within an extensive parametric study developed for different isolator and system properties, fragility curves of both the pier and isolation system supporting the deck are evaluated. In line with the hazard curve of the reference site, the corresponding seismic reliability curves are computed by means of the convolution integral. Finally, seismic reliability-based design abacuses for different structural properties are proposed.

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Paolo Castaldo, Guglielmo Amendola, Luca Giordano, Elena Miceli.