Effect of FRP retrofit interventions on seismic vulnerability of existing bridges

Bridges are the one of the most vulnerable elements in existing road and railway networks dur- ing earthquakes, hence the assessment of their seismic vulnerability and the study of the techniques to reduce it are common issues in the general context of the management of the transportation network. One of the most diffused method to evaluate seismic vulnerability of existing bridges is based on the calculation of the fragility curves, which give the probability of a bridge reaching a certain damage state for a given ground motion pa- rameter. By means of fragility curves, damage of critical elements of the bridge can be predicted and conse- quent economic losses can be estimated. Moreover retrofit interventions can be planned. In this framework fragility curves for a bridge having a common structural scheme in Italy (multi-span simply supported reinforced concrete bridge) have been calculated by means of non-linear dynamic analyses. Then the influence of methods to reduce seismic vulnerability of the bridge by pier confinement with fiber- reinforced polymers (FRP) was studied. Theoretical models for the evaluation of the constitutive law of con- fined piers were developed to generate the fragility curves of the bridge taking retrofit effects into account.