CORROSION MODELING STRATEGY IMPACT ON EXPECTED SEISMIC LOSSES FOR RC BRIDGES-A CASE-STUDY

Recently observed bridge collapses in Italy highlighted their necessity to be analyzed and eventually retrofitted, as a consequence of the seldom regular maintenance interventions on existing bridges. Within such a context of ageing structures, corrosion of reinforcement represents one of the major threats that can further reduce the residual life/capacity of reinforced concrete (RC) bridges. This can be even more detrimental for bridges located in earthquake-prone areas, indeed their seismic performance are affected. In this sense, this study investigates the seismic response of a typical RC bridge subjected to increasing levels of corrosion to enhance the understanding of their life-cycle performance, and guide future design and maintenance of bridges. To this end, multi-stripe analysis using finite element (FE) models is carried out to investigate their dynamic behaviour under seismic loads. Different corrosion modeling strategies of increasing complexity are considered to understand how detailed the modeling should be without losing accuracy. To this end, results are expressed in terms of fragility curves and expected seismic losses, which are very important for bridges. It is observed how corrosion may reduce bridge performance under seismic loads and increase expected annual seismic losses, as expected. On the other side, it is shown that using the simplest way of modeling corrosion, i.e. through the sole reduction of reinforcement cross-section area, will produce results very close to the ones carried out using more advanced modeling that accounts for ductility and strengths reduction of steel as well as the degradation of the concrete properties surrounding reinforcement.