Collapse analysis of the multi-span reinforced concrete arch bridge of Caprigliola, Italy

On April 2020, the 260 m-long reinforced concrete (RC) arch bridge of Caprigliola (Massa and Carrara, Italy) suddenly collapsed into the Magra river. In this work, aimed at investigating potential reasons behind the observed failure, a numerical study is conducted using the Applied Element Method (AEM), which allows the explicitly modelling of damage propagation and progressive failure up until complete collapse. Both local and global models of varying levels of detail have been developed and the consequences of different possible failure scenarios induced by selected potential triggering factors are compared with publicly available forensic evidence. Although only cross-correlations against future official post-collapse reports, currently not available, might permit the establishment of more definitive conclusions on the causes behind the observed collapse of the bridge, a seemingly good agreement was nonetheless found between predicted and observed damage and debris distribution for one of the modelled scenarios (induced movements of one of the bridge piers/abutments), which may thus be deemed as potentially more plausible than the others.