Structural behaviour of old reinforced concrete bowstring bridges affected by corrosion

Many reinforced concrete bridges constructed in Italy between the 1930s and 1960s on secondary roads display a distinctive bowstring design. This configuration features an arch with no horizontal thrust, wherein the arch, the girder, and the connecting components, namely the hangers, are all composed of reinforced concrete. In some variations, the bowstring arch incorporates diagonal elements, forming a truss structure with a curved upper chord. Many of these bridges are now nearly 100 years old and exhibit high levels of corrosion with rather poor quality of the original materials. However, it is interesting to note that in these cases, even with high levels of degradation, these bridges maintain a significant safety factor. Based on an emblematic case study, the behavior of such bridges is investigated both in the original and degraded states, to evaluate the structural behavior and robustness they exhibit, and to inform decisions regarding whether to demolish and rebuild or to rehabilitate these historic bridges, which are now at the end of their service life.