A preliminary methodology for multi-hazard risk assessment of large bridge portfolios using quantitative indicators

Abstract

In the last years, several catastrophic collapses of existing bridges have raised growing awareness to the need for structural assessment, health monitoring, and retrofitting by public institutions and infrastructure management entities. Several issues, such as limited knowledge of existing bridge structures, exposure to multiple hazards, or deterioration, make risk assessment and decision-making on existing bridges a challenging task, especially when qualitative approaches are used for risk prioritization. This study proposes a methodology for quantitative risk assessment of existing bridges, considering the large-scale analysis of bridge portfolios under natural and anthropic hazards, and the impact of their out-of-service/collapse on the road network. Specifically, a rational risk-based ranking of large bridge portfolios is obtained to identify the most critical ones, which are subject of further detailed analysis. Four available methods in the literature are used to assess the structural condition and the seismic, fire, and impact risks for a stock of twenty bridges located in northern Italy. The individual risk indicators are then combined to obtain a total multi-hazard risk indicator (IMH), while studying different combination approaches being compared one each other. Finally, the obtained results are compared with those obtained according to the Italian guidelines, which rely upon more qualitative approaches that are not so easily usable for risk prioritization from management entities.