Corrosion Fatigue Investigation on the Possible Collapse Reasons of Polcevera Bridge in Genoa

On August 14, 2018, a few spans of the cable-stayed viaduct crossing the Polcevera river (Genoa, Italy) collapsed, causing tens of fatalities along with considerable material damage and hundreds of people displaced. The viaduct, as well as many others belonging to the AQ1 national road network, was built in the second half of the last Century, and has been in service for over fifty years. In the present paper, a possible scenario is proposed to put into evidence how the combined effect of fatigue at very-high number of cycles and corrosion could have been responsible for the sudden failure of one of the strands and the subsequent collapse of the so-called balanced system conceived by the designer Morandi. The analysis accounts for an actual estimation of the heavy lorries traffic and load spectrum, as well as the European standards prescription for the fatigue damage accumulation assessment. In addition, the effective construction phases of the viaduct are considered. The structural analysis is carried out by means of analytical models, in order to simplify the structure complexity without prejudice to the description of the most relevant aspects of the structural behaviour. The purpose of the present study is not to identify responsibility among the different actors involved with the infrastructure collapse, aspect to be addressed by the Italian magistracy. On the other hand, the main goal is to warn the scientific community and the public administrations that the combined effects of low amplitude fatigue and corrosion can be dangerously underestimated, and that the existing asset of last Century bridges deserves special attention in this respect