The corner failure in a masonry building damaged by the 2016-2017 Central Italy earthquake sequence

Although still poorly investigated, the failure of corners is a frequent event in masonry buildings and clearly recognizable in the aftermath of a seismic event. It is characterized by the formation of a masonry wedge, mainly due to the thrust of roof elements in addition to inertial forces, and it generally involves rocking-sliding motion along the cracks on the interlocked orthogonal walls. In this paper, the case study of the corner failure in a masonry building located in Visso (Italy) is analyzed. The building was seriously damaged by the seismic events of August 24th, 2016 and October 26th and 30th, 2016. In particular, one of the free corners at the first storey completely collapsed. The seismic capacity with respect to the onset of this failure mode is analyzed by means of a refined macro-block model and by adopting the linear kinematic approach of limit analysis, accounting for frictional resistances and the thrust of roof elements. The key aspect of the proposed approach is the introduction of a criterion to evaluate the contribution of the actual frictional resistances depending on the inclination angles of the crack lines. Moreover, the loads transmitted from the roof to the walls are defined by assuming simplified static conditions according to the typology of the hipped roof. Lastly, the achieved results are compared to the seismic demand obtained by adopting the Italian Technical Standards for Constructions, both the earlier version (2008) and the current one (2018), together with that obtained using in situ recorded floor accelerations