Fatigue assessment of the collapsed XXth Century cable-stayed Polcevera Bridge in Genoa

Abstract

The present paper investigates the combined effect of corrosion and fatigue at very-high number of cycles on the recently collapsed Polcevera Bridge. Since the construction, in the mid-sixties, the viaduct has experienced a dramatic increase in the heavy lorries traffic. Although the amplitude of stress oscillation in the strands was limited, it is assessed that the number of larger load amplitude cycles reached eighty million, out of almost half a billion of total vehicles that crossed the bridge. Due to the aggressive environment, the degradation of the bridge has developed much faster than expected. It is likely that, already at the beginning of the Eighties, the effectiveness of the prestressed concrete covering of the strands was vanishing in some sections close to the antenna, both in terms of protection and local stiffness. As a result, the levels of corrosion detected in the strands could have been sufficient to trigger the brittle failure of one of the stay cables, and the subsequent collapse of one of the self-standing structural systems. Besides to figure out the possible collapse mechanism of the Polcevera Bridge, the authors wish to rise the attention of the scientific community on the rather underestimated phenomenon of very-high cycle corrosion fatigue in existing civil infrastructures.