Experiences from the Northern Italy 2004 earthquake: Vulnerability assessment and strengthening of historic churches

This work is about the lesson learnt from the analysis of the damages caused to some churches by the strong earthquake, which struck Northern Italy in the year 2004. Focus is paid to some mechanisms which are not well known in the literature: the excessive and differential rocking of neighbouring transverse arches, the differential deflection of single leave vault rings, the tie over-tension induced by the transverse arch rocking. In the paper, the structural solutions appositely studied to repair and to reduce the structure seismic vulnerability of these buildings are presented. Among these solutions: internal perimeter ties, lightweight wooden roof box structure, lightweight spandrel ribs are illustrated.