Seismic vulnerability for churches in association with transverse arch rocking

The research work stems from the surveys and the analysis of the damages surveyed in several churches following the 2004 earthquake in northern Italy. Focus is paid to the rocking of the diaphragm arches, which frequently induced significant damages, such as yielding or failure of the tie rods and, in one church, the collapse of the nave vaults. The diaphragm arch-rocking collapse mechanism is studied referring to the limit analysis approach, taking into account the phenomena involved, such as the buttress action of the abutments and the confining action of the tie rods. The analytical evaluation of the collapse multiplier in the case of either over-resisting or weak ties is proposed. The analytical model is validated by comparison with the experimental behavior of an arch-to-abutment structure subjected to rocking. As an example, the analytical model is applied for the structural vulnerability assessment of two churches, which were severely damaged by the 2004 earthquake.