Reliability Analysis of Seismic Isolation in Retrofitting of Simply Supported Bridges

The paper investigates the reliability of simply supported bridges, retrofitted or less with seismic isolation, by means of fragility curves, which represent the probability of reaching a certain damage level for an assigned seismic intensity. Taking advantage of the Multi Stripes methodology, several nonlinear dynamic analyses of a multi-span bridge representing the existing ones in Italy built in the 60 ' characterized by means of non linear finite element models in different design configurations of seismic retrofit have been carried out, in order to obtain the fragility functions.The obtained results allow to assess the isolation retrofit strategies effectiveness to mitigate the seismic risk of simply supported bridges, highlighting the influence of different design strategies on the probability of exceeding the limit states considered