Abstract

This study concerns a new probabilistic framework to evaluate road/railway bridges after an earthquake by means of analytical fragility curves and inspections on the structure. In particular, the assessment is performed on existing reinforced concrete (RC) bridges with a common structural scheme in Italy (multi-span simply supported girder bridges). The framework is set up of 6 steps and each step is investigated. Steps 1 and 2 are a sort of preliminary work before the seismic event occurs: the creation of a database to collect all information about bridges in specific road/railway networks (step 1) and the generation of fragility curves for each bridge (step 2): fragility curves are instruments describing the probability of a structure being damaged beyond a specific damage state for various levels of ground shaking. Since step 2 is a crucial step for the outcomes of the framework, a wide investigation on the generation of fragility curves is presented, considering bridges located in strategic road network points in Veneto region (North-Eastern Italy) and different numerical modellings, in order to evaluate the best seismic vulnerability assessment. Moreover, particular attention is given to retrofit interventions by means of Fiber Reinforced Polymer (FRP) and their effect on bridge seismic vulnerability reduction. The other steps concern activities to carry out after a seismic event, useful for emergency and post-emergency phases. Step 3 regards a method to decide if inspections on bridge are needed in relation to the occurred earthquake seismic intensity; if the seismic intensity measure reaches a specific threshold, step 4 suggests how to perform visual inspections on bridges, under a probabilistic point of view, and to generate the damaged bridge fragility curves. After that, the last two steps try to give useful information to Institution and owners of bridges in order to reach an optimal road/railway network management in post-earthquake phases. Step 5 concerns a quick procedure to decide whether or not allowing traffic over damaged bridges, whereas step 6 gives information about economical benefits coming from a comparison between replace costs and retrofitting costs (considering FRP retrofitting interventions) of damaged bridges. In order to clarify the framework procedure, an example for each step is developed.