Risk Assessment of a Railway Bridge Subjected to a Multi-hazard Scenario

Bridges present valuable assets for the rail and road network by providing cross at critical links such as waterways, valleys, and other types of facilities. However, these types of structures are exposed to several threats during their life-cycle such as natural hazards and deterioration, which compromise their performance. To assess the condition state of such infrastructure and define maintenance and mitigation strategies, several performance indicators of quantitative nature have been proposed during the last decades by several researchers. Among those indicators, risk has received great attention as it enables to account for both the performance of infrastructures subjected to hazard events, and the consequences associated to an inadequate level of service of the infrastructure. Nevertheless, risk is not a stationary indicator, i.e. several parameters involved in the estimation of risk are time-dependent. One of them comprises the structural capacity of infrastructures, which is affected by deterioration effects over time. This gradual deterioration can be regarded as an interceptable hazard, which may act simultaneously with other non-interceptable hazards such as natural events (e.g. earthquakes). Therefore, a risk assessment framework should account for the probability of having these multiple hazards acting during the service life of infrastructures. The aim of this paper is to conduct a risk assessment for a railway bridge subjected to a multi-hazard scenario, i.e. an observable interceptable hazard corresponding to chloride induced corrosion of the reinforcing steel in reinforced concrete elements, together with seismic hazard. The results of the study demonstrate the relevance of considering time-dependent deterioration effects on the risk assessment of bridges, as the increase in the seismic fragility over time is significant. These findings are relevant for decision-making to plan and execute optimal interventions.