Arch Concrete Bridge Risk-Based Assessment Using a Portuguese Case Study

The chapter presents a detailed risk-based assessment of the Cró Bridge in Portugal, a reinforced concrete arch bridge carrying a national road. It first introduces the importance of road infrastructure and the complexity of quantifying its economic benefits. The study focuses on the Cró Bridge, built in 1940 and repaired in 2010, using data from design projects and inspection reports. Hazards are categorized into natural events like floods and seismic activity, and structural degradation processes. Floods are identified as a significant natural hazard, with the Cró River presenting a low risk of flooding but potential scouring effects. Seismic hazards are moderate-low in the Guarda region. Structural degradation is evident from inspections, with defects such as concrete spalling, hairline cracks, and steel corrosion observed. The risk evaluation focuses on economic consequences, including replacement and repair costs, traffic delay costs, and fault tree analysis. Quantitative risk assessment reveals that the highest risks are associated with deck failure due to overloading and foundation failure due to scour. The chapter concludes by recommending a quality control plan to mitigate structural deterioration, highlighting the need for ongoing maintenance and monitoring of the bridge.